Mares Avanti Quattro Plus Adjustable Heel Strap Fins with Dive Mask Channel Thrust Technology system for optimal water channeling Maintaining optimal thrust throughout every phase of the finning stroke minimizes fatigue Quick release, quick-adjust buckle makes adjusting a snap Soft anatomical foot pocket, with ribbed insole for an improved fit and a dramatically more efficient fin stroke ABS (Adjustable Binding System) Fin Buckles - one finger release