The aqua sphere zip vx fins are a great piece of swimming equipment ideal for all swimming levels and activities the natural kicking motion helps improve swimming efficiency and the holes in the blades create vortices which increase thrust thanks to the narrow blades your muscles will tire slower and you can improve the mechanics of your kicking the flippers offer a custom fit with easily adjustable buckles and the non slip pads on the fin rails mean more traction for a better push off the w