C4 Carbon - Protech Freediving Fins

C4 PROtech Freediving Fins

The C4 PROtech Freediving Fins are high-performance carbon freediving fins built for divers who want efficient propulsion, precise blade response and a secure anatomical foot pocket connection.

C4 designed the PROtech around a complete blade-foot pocket system: a multilayer carbon blade, a right/left anatomical foot pocket, a monoblock blade-foot pocket structure and a hydrodynamic geometry developed for smooth, technical and efficient finning.

The result is a versatile carbon fin for depth training, CWT, open-water freediving, pool training and regular freediving sessions — powerful enough for serious progression, but still comfortable enough for frequent training.

Why choose the C4 PROtech?

Many carbon fins are built around the blade first and the foot pocket second. The PROtech takes a more integrated approach. C4 combines the blade and foot pocket into a connected performance system designed to reduce energy loss and improve force transfer from the foot into the carbon blade.

The PROtech is not an extreme specialist blade for one narrow use case. It is a modern, comfortable and efficient carbon fin for freedivers who want reliable performance across pool training, depth sessions and open-water dives.

Main benefits

• Multilayer carbon blade for responsive and efficient propulsion
• Medium / soft blade response for comfort, control and regular training
• Right/left anatomical foot pockets for a more precise and natural fit
• Monoblock blade-foot pocket structure for direct thrust transmission
• 3D hydrodynamic geometry designed for fluid movement through the water
• Controlled buoyancy for better trim and stability in pool and depth sessions
• 29° blade angle for efficient kicking mechanics
• Rounded water rails for clean water channeling along the blade
• Excellent all-round use for training, CWT, depth sessions and open-water freediving

Carbon blade performance

The PROtech blade is designed to give a smooth, progressive and predictable response. It is not an ultra-stiff competition blade that only works for a narrow group of athletes. Instead, the medium / soft setup gives a strong balance of comfort, efficiency and usability.

This makes the PROtech especially interesting for freedivers who want their carbon fins to be used regularly — not only for rare maximum-depth attempts. The blade response is forgiving enough for training, but still clearly more efficient and responsive than entry-level polymer fins.

The 29° blade angle supports a natural kicking position, while the rounded water rails help guide water along the blade for a cleaner and more stable finning movement.

Built around the C4 anatomical foot pocket

The foot pocket is one of the most important parts of a freediving fin. If the foot pocket is too loose, power is lost before the blade reacts. If it is too tight, comfort and relaxation suffer.

The PROtech foot pocket is designed to wrap the foot more naturally, with a right and left shape instead of a generic symmetrical design. This improves comfort, reduces unnecessary movement inside the pocket and supports better power transfer during the kick.

A secure foot pocket does not just feel better. It makes the blade work better. The less your foot moves inside the pocket, the more directly your kick transfers into propulsion.

Foot pocket size guide

The C4 PROtech foot pocket size should not be chosen by shoe size alone. For the best fit, measure your foot length and the two foot circumferences used in the official C4 PROtech size chart.

The official C4 guide uses three key values:

• L = foot length from heel to big toe
• CA = foot circumference at point A
• CB = foot circumference at point B

The PA and PB values in the table show where to measure Circumference A and Circumference B from the big toe. The listed circumferences refer to compatibility with the internal shape of the foot pocket. For an optimal fit, your foot circumference should generally be slightly larger than the indicated value, depending on intended use and preferred tightness.

If you are between sizes, use thin neoprene socks, toe protectors or contact us before ordering. Foot pocket fit is too important to guess.

Recommended accessories

For the best comfort and fit, pair the PROtech fins with thin socks or toe protectors depending on your foot pocket fit.

• C4 0.5 mm Open Heel Socks: best if the foot pocket already fits well and you want more comfort during longer sessions.
• C4 0.5 mm Toe Socks: best if you want minimal toe protection and better hold in the front of the pocket.
• C4 1.5 mm Toe Socks: best if the toe area has slightly too much space or you want a stronger fit adjustment.

Technical details

Availability

The C4 PROtech is available in multiple foot pocket sizes. To provide access to the full size range, not every size is permanently stocked at our warehouse.

If your preferred size is not immediately available, typical delivery time is approximately 7–14 days. Contact us before ordering if you want to confirm current availability.

Kaluna Freediving Opinion

The C4 PROtech sits in a very useful position: it is a real carbon fin, but not an overly stiff specialist competition blade. For many freedivers, that makes it more practical than a harder, more demanding setup.

The strongest argument is the complete C4 system: anatomical right/left foot pockets, monoblock blade-foot pocket construction and a medium / soft carbon blade that can be used regularly in training.

If you want maximum stiffness for pure competition use, there are more specialized fins. If you want a comfortable, efficient and modern carbon fin for real-world freediving training, the PROtech is one of the most compelling options in this price range.

FAQ