Phantom Aquatics Speed Sport Adjustable Snorkeling Fin Extended Sole Plate Adds Thrust and Relieves Strain on Foot Simple and Reliable Strap Adjustment System, Easy to Don and Doff Contoured Foot Pocket for Maximum Comfort, Use with or without Booties High Grade Polypropylene Material, More Thrust Per Kick with Efficient Energy Transfer Structurally Optimized Hinge Point Provides Correct Fin Shape Throughout Kick Cycle