Technical sheet

C4 Unit 400 Footpocket

Q: Hello, I want to buy this calco n 41 brazil boiler which size should I buy

Hello,Please take into consideration that Brazilian sizes are different, with a difference of about 2 sizes.Therefore, you should opt for the size EU 42-43. If you plan to wear 5mm socks you should even go a size higher.Best regards

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29 Reviews

5 Questions

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Features of C4 Unit 400

Product description of C4 Unit 400 Footpocket

Description summary

Experience the revolutionary C4 400 Footpocket, the lightest on the market at just 390 grams. Engineered for freedivers and spearfishermen, its ultra-light design dramatically reduces fatigue, allowing for longer, more comfortable dives. The ergonomic shape with a 3-degree angle ensures a biomechanically correct kick, maximizing power transfer and minimizing strain on joints. Crafted from durable thermoplastic rubber, it offers a secure, responsive fit for ultimate control and efficiency. Upgrade your fins and feel the immediate difference in performance and comfort

Discover the revolutionary C4 400 Footpocket, a new benchmark in lightweight performance and ergonomic design for the discerning freediver and spearfisher. Engineered to elevate your underwater experience, the 400 foot pocket is the result of meticulous research and development, embodying the pinnacle of C4’s innovative style and commitment to excellence.

At the heart of the 400´s design is an unparalleled focus on weight reduction. We are exceptionally proud to introduce what are currently the lightest thermoplastic rubber foot pockets available on the market. Thanks to a unique and sophisticated design, each foot pocket weighs an astonishingly low 390 grams. This dramatic reduction in weight is a game-changer for underwater propulsion. It directly translates to significantly reduced fatigue in your legs and ankles, allowing for longer, more comfortable dives and conserving precious energy with every kick. You´ll experience less strain and more endurance, whether you´re exploring the reef or targeting your next personal best.

Comfort has not been sacrificed for lightness; it has been enhanced. The C4 400 features a distinct, ergonomic design that is a hallmark of the C4 philosophy. Central to this is the integrated pre-formed 3-degree angle. This subtle but critical feature aligns the blade with the natural posture of your foot and leg, promoting a more efficient and biomechanically correct kicking motion. This intelligent engineering ensures maximum power transfer from your leg to the fin blade, improving overall efficiency while drastically reducing the risk of discomfort or cramping in the ankle and knee joints, even during extended sessions in the water.

Manufactured from a high-quality thermoplastic rubber, the 400 foot pocket provides the perfect balance of flexibility, durability, and responsiveness. Its unique structure is engineered to comfortably cradle your foot, ensuring a secure and responsive fit that feels like a natural extension of your body. This allows for precise control over your fin blades and an immediate transfer of power, giving you the agility and thrust you need, exactly when you need it. Upgrade your fin setup with the C4 400 and feel the immediate difference in performance, comfort, and efficiency.

Important Information:

* This product is sold as a single item (1 unit).

Specifications

Manual

Size chart

Technical specifications of C4 Unit 400

Features of C4 Unit 400

Color Black

Color

Black

Key differentiators

Ergonomic construction with a preformed 3-degree angle for comfort and efficiency.

Lightweight design at just 390 grams for reduced fatigue.

Made from thermoplastic rubber for a secure, flexible fit.

Versatile use, suitable for wearing barefoot or with neoprene socks.

Technology in C4 Unit 400 Footpocket

Energy rating

Warnings

4.9 / 5

29 Reviews

What our customers are saying about C4 Unit 400 Footpocket

The C4 400 foot pocket is praised for its excellent quality, lightweight design, and comfort. A significant upgrade from the C4 300, it´s much softer and easier to put on. The material is a perfect compromise between firm and flexible, providing an efficient, secure fit that doesn´t flutter. It´s versatile for use barefoot or with neoprene socks. Sizing can be tricky; many recommend sizing down for barefoot use as the fit can be large

Satisfied

2025/05/20

Sandy

I originally had a C4 300 foot pocket, which was difficult to put on and take off. I replaced them with C4 400s to use with my Red Fox paddles. They're heaven-sent, easy to put on and take off. I always lubricate them with soap to make them easier to put on. Recommended

Very comfortable FP

2025/02/27

Oleksandr

I like this model, it's absolutely good for this cost

Good shoe

2024/03/02

Mauricio

It is an excellent product for the price, it is not as elastic as others but once put on it is quite comfortable and light, highly recommended if you are looking for a good pocket pocket at a low cost.

Very light but be careful for the size

2024/02/22

Aki

My shoe size is US 6 so I bought 36-37. With 2mm socks, the length is perfect fit, but since the opening around ankle and toe is also small and there is not much stretch, it was almost impossible to wear without shoehorn. So be aware if you have tiny feet, you may need to size up. Other than that it's good quality and very light.

C4 400 fitting

2023/06/09

Jose Manuel

The same quality as always in C4. It fits perfectly to the foot and its elasticity allows it to be worn barefoot or with a 3mm bootie. Not once has it fluttered loose on me

Good quality c4.

2023/05/30

N. Gomes

Already used before, it is a good quality footpocket. Quick send.

Good product

2022/12/18

Catalin Adrian

All perfect! Excellent C4 quality! Very comfortable, easy to put on. I recommend it!

Great pocket

2022/11/04

Jochen

I only use C4 Pockets, in several sizes, with and without neoprene socks. The fit is great for me, the 400 material is the perfect compromise between firm and elastic. I think the light weight and the slim, elegant design are great

Good ^^

2022/10/21

eui seok

I love it so much~~~~~~~~~~~~

C4 feet

2022/09/27

Nuno Barbosa

Great quality material. Very soft.

C4 400 foot pocket

2022/08/22

Only bought 1 piece to test the size. Not tested in water

Slipper c4 400

2022/08/19

jerome

very large slipper take a size down

We'll see how long these last!

2022/08/10

Rodrigo

Already put the spare, I'll see how long you last. Thanks for sending everything ok!

Excellent quality!

2022/07/06

Amorim

Excellent C4 quality! Very comfortable, easy to put on and efficient. I recommend it 100%.

received item

2021/12/21

songbin km

yesterday I received item! it is ggod as same as described!

Very well

2021/09/20

Stefano

All perfect! Product and shipping to 100.

Perfect

2021/08/21

Ellington

The best footpockets for me. Good fit, a little more flexible than the 300.

C4 400 foot pocket

2021/07/24

Janneke

Nice foot pocket. The 300 model cuts into my skin, on the other hand, it is much softer on the skin and you can also wear it without socks. The size is normal. I normally have a size 40 and the size 40/41 I can handle well with 3mm socks as well as with bare feet and fin binders

Very light

2020/09/25

LI JUN

Very light

C4 400

2020/09/23

wang Yu Hsiang

good quality and good price

Perfect fit

2020/08/19

the pockets came large. I ordered for the size of my feet. But I went and bought 5mm socks and they fit perfect. If your not going to wear socks. Order a side smaller maybe

C4 400

2020/05/29

ILYA

On 43, size 44-45 fits with a toe of 3-5mm. Without fastener.

C4 400

2020/04/02

Max

Very good shoe, but if you want to wear it barefoot, you have to take size smaller. I have mat 44.5-45 For bare feet, 42/43 fits perfectly. With thicker neoprene shoes 44/45.

I like

2020/03/14

Alexander

The galosh is comfortable and light, I liked it! Shipped and delivered on time! I can only recommend)))

Fast delivery, great item

2020/01/31

Ростислав

It came very quickly, excellent galoshes, though in a big way!

Galoshes

2019/10/21

Иван

Great galoshes.

С400 foot pockets

2019/09/23

Konstantin Anokhin

С400 foot pockets. The product is made with high quality. Fit to size. My size is 42-43. Ordered 44-45. A 5 mm neoprene toe is normal. Dress up lighter than the C300. Although they are heavier than the C300. Delivery is fast enough, about a couple of weeks. Thanks.

a average satisfaction

2019/06/27

cedric

don’t seem to stretch that much and heavier than 300

Excellent galoshes

2019/05/25

Unlike the 300 model, these galoshes are not so difficult to wear. I would recommend the previous one for warm water and competitions. This model is perfect for underwater hunters and cold water.

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Include AI Generated questions and answers

2022-08-18

Aidar

Hi, is it a pair or single?

Answer of Gregory

Correction: I bought a pair but it is sold individually.

* Generated by AI based on customer and product data

2024-01-11

Martin Z

Hello, are these foot pockets compactible with C4 400 FAST blades?

Answer of Bonaventura

I think yes. I used them on different blades.

Answer of CARLOS

Yes. They are compatible with C4 Fast 400 blades.

Answer of STEPHANE

Hello, Yes compatible

Answer of David

Yes, in fact they are the ones that come in those shovels when you purchase the complete ones.

* Generated by AI based on customer and product data

2024-02-20

Edinei de oliveira

Hello, I want to buy this calco n 41 brazil boiler which size should I buy

Answer of Dominique Reynaud

Hello, Please take into consideration that Brazilian sizes are different, with a difference of about 2 sizes. Therefore, you should opt for the size EU 42-43. If you plan to wear 5mm socks you should even go a size higher. Best regards

* Generated by AI based on customer and product data

2024-06-29

Alvaro

For a foot size 42, do you recommend the 42/43? And if so, when will you be available?

Answer of Bonaventura

Good footpocket’s. I would buy them again. 42/43 available at the moment

Answer of khalil

When your feet size is 42 you need to buy 42, fits well light I like it for the price.

Answer of Cristian

Im 42/43 I was.large and I also have 42 feet. And so I got a munero less and I´m happy with the 1.5 mm shoe.

Answer of David

Yes, I have that foot size and I have that size, prefects.

* Generated by AI based on customer and product data

2024-09-18

Pablo

Would the C4 400 foot pocket be compatible with the C4 carbon s990 blades?

Answer of Bonaventura

I used it on dessault fast by C4 blades and fits perfectly. S9900 and fast dessault are pretty different so i think not.

Answer of STEPHANE

Yes compatible.

* Generated by AI based on customer and product data

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Frequently bought together

Best sellers

Use cases

Upgrading or Repairing Freediving/Spearfishing Fins 90% Fit

As a standalone component, this footpocket is ideal for divers who need to replace a damaged pocket or upgrade their existing setup. Its lightweight design and thermoplastic rubber construction offer a great balance of comfort and performance for custom fin builds.

Lightweight construction (390 grams),Thermoplastic rubber material,Ergonomic 3-degree angle

Long Freediving Sessions 80% Fit

The ergonomic design, featuring a 3-degree preformed angle, is intended to improve comfort and efficiency during extended dives. The thermoplastic rubber is versatile, allowing for use with or without neoprene socks to suit water temperature and personal preference.

Ergonomic 3-degree angle,Versatile for use with or without socks,Lightweight design

Spearfishing 75% Fit

For spearfishing, a secure and comfortable footpocket is essential for control and power. The firm yet flexible thermoplastic rubber construction provides stability, while the lightweight nature helps conserve energy during stalks and dives.

Thermoplastic rubber material,Lightweight construction (390 grams),Ergonomic design

Casual Snorkeling 60% Fit

While designed for more demanding activities, this footpocket can be used for casual snorkeling when paired with an appropriate blade. Its comfort-oriented features, like the ergonomic angle and versatile fit, make it a reliable choice for recreational users building their own fins.

Ergonomic 3-degree angle,Lightweight design,Versatile for use with or without socks

Best for

Best for Freedivers Seeking Efficiency

The lightweight design and preformed 3-degree ergonomic angle provide efficient propulsion and control, crucial for deep dives on a single breath.

Ergonomic design angle: 3 degrees; Fin weight: 390 grams

Ideal for Agile Spearfishing

The thermoplastic rubber construction offers a firm, flutter-free fit for enhanced stability and control when maneuvering to track and hunt underwater.

Materials: thermoplastic rubber

Great for Casual Diving Comfort

Designed for an easy fit, this softer footpocket can be worn barefoot or with neoprene socks, ensuring comfort during infrequent recreational dives.

Perfect for Comfortable Snorkeling

Its lightweight build and easy-to-put-on design make it a comfortable and practical choice for relaxed snorkeling sessions close to the surface.

Fin weight: 390 grams

Benefits

FunctionalErgonomic Design for Enhanced Comfort

Experience superior comfort during your dives with a footpocket designed for an optimal fit. The preformed 3-degree angle and ergonomic construction reduce strain, allowing for longer, more enjoyable underwater sessions.

Ergonomic design angle: 3 degrees

Materials: thermoplastic rubber

Ideal buyer profiles

The Spearfishing Adventurer

This diver is focused on performance, efficiency, and reliability for demanding spearfishing activities. They require gear that provides excellent control for precise movements and efficient propulsion to conserve energy during long hunts.

The C4 Unit 400's lightweight 390-gram construction and preformed 3-degree ergonomic angle enhance propulsion efficiency, reducing fatigue. Its thermoplastic rubber build offers a firm, non-fluttering fit, ensuring superior control and stability for confident maneuvering underwater.

The Freediving Enthusiast

This individual seeks to maximize their depth and bottom time on a single breath. They prioritize hydrodynamic efficiency, comfort for prolonged use, and a secure fit that translates every movement into powerful propulsion.

Weighing only 390 grams, this footpocket minimizes drag and energy expenditure. The ergonomic design, featuring a 3-degree angle, is engineered to optimize kicking mechanics for speed and efficiency, while the soft thermoplastic rubber ensures a comfortable fit for extended freediving sessions.

The Occasional Diving Hobbyist

This user enjoys recreational diving and snorkeling but values comfort and ease of use above all. They want reliable gear that is easy to put on and comfortable for various water conditions, whether worn barefoot or with socks.

This footpocket is made from a soft thermoplastic rubber that is easy to put on and comfortable for extended wear. Its versatility allows for use either barefoot or with neoprene socks, making it adaptable for different temperatures and preferences, which boosts confidence for recreational dives.

Competitive features

The C4 Unit 400 Footpocket is a specialized component designed for divers who build or customize their own fins. Unlike the complete spearfishing fin sets it's compared against, such as the Seac Booster and Imersion Challenger Pro, the Unit 400 is sold as a standalone footpocket. This comparison focuses on its unique characteristics and how it stands as a component option against integrated fin systems.

Where it excels

The C4 Unit 400 is exceptionally lightweight, weighing only 390 grams, making it one of the lightest thermoplastic rubber footpockets available. Engineered with a preformed 3-degree angle, it's designed to enhance comfort and swimming efficiency. It offers a versatile fit that can be used comfortably either barefoot or with neoprene socks, providing a secure hold without fluttering.

Consider alternatives if...

If you are looking for a complete, ready-to-use fin set out of the box, integrated options like the Seac Motus or Imersion E: Spearfishing Fins would be more suitable, as the C4 Unit 400 is a footpocket only and requires a separate blade and assembly kit.

Verdict

The C4 Unit 400 Footpocket is an excellent choice for experienced divers, freedivers, and spearfishers who prioritize customization, comfort, and a lightweight setup. Its unique design offers a notable upgrade in comfort and efficiency. However, it is a component, not a complete fin, making it less suitable for those seeking a simple, all-in-one solution. Its price point is competitive for a high-quality, specialized footpocket.

Specs comparison