The foot pockets for fins are of various types. Very interesting are the Salvimar Delta One K-Reinforced, the anatomic C4 and the Pathos. Let’s start with the first ones.
Thermoplastic or natural rubber, traditional or super anatomic shape, differentiated thicknesses or inserts inside the rubber: many are the solutions on the market. It is important to know that, especially if ones uses high performance (and cost) blades, such as the ones in carbon fiber, it makes no sense to use low quality foot pockets, which are no able to transmit properly the force generated by the leg and foot of the spearo or freediver. For high performance blades we need good level foot pockets, both on material and design side. Very interesting is the Salvimar Delta One K-Reinforced solution. If on one side C4 has revolutionized the market with super anatomic and asymmetric foot pockets, with also a revolutionary connection to the blades, and Pathos, who has designed foot pockets specifically for carbon fiber blades.Salvimar has put a lot of work studying on a traditional shape, but optimizing materials and geometry.
The Delta One K-Reinforced foot pocket first of all is made of 55 Shore hardness natural rubber, a material that maintains mechanical characteristics (hardness and elasticity) along time, without deforming or hardening. Moreover, natural rubber, diversely to thermoplastic, does not present great variations of its hardness with temperature. It is in fact true that many low quality foot pockets become very hard in Winter with very low water temperatures (10-15°C), while they become too soft in Summer, with sea water temperature over 25°C. The longerons are instead of 80 Shore rubber, to give more consistency to the lateral connection to the blade.
The top of the line foot pocket by Salvimar (also a more economical version exists, named « Step« ) has as extremely innovative and intelligent element a Kevlar band inside the rubber, at the height of the instep, exactly where most of the push is transmitted from the foot to the foot pocket to the blade. Since Kevlar does not elongate, in fact, the foot pocket on the instep, even though bit remains soft thanks to a not too hard rubber, transmits all the push possible to the blade. From this solution comes the name K-Reinforced.
To the above innovative solution others are added, such as the different thickness rubber in different area. To do this the manufacturing process sees a stamping of the upper part of the foot pocket and an injection for the lower part. Finally, the foot pocket is complete with a special connecting system with the blade that insures the perfect matching between the two parts, thanks to a plastic insert that reduces any tolerance.
The rear part of the foot pocket has a V shape to help insertion of the heel.