The Avanti Superchannel by Mares is designed with an open heel and bungee strap to produce a fin which is both comfortable and powerful. The blades have a large channel running down their centre and two smaller channels adjacent to direct water and provide thrust efficiently so you don't fatigue as quickly. The blades are made from thermoplastic rubber and tecralene to create regions of rigidity and flexibility for ideal responsiveness to kicking. The bungee strap of the fin means you don't have to adjust the fin strap, instead it naturally stretches to your size and maintains a firm hold. This makes donning and doffing the Avantis easy. Mares Avanti SUPERCHANNEL features: Three channels direct water for maximal thrust Dual material construction of the blades for ideal flex and responsiveness Elastic bungee heel strap for easy fitting and donning and doffing Resistant to chemical and UV wear Large hand loop for easy application and removal