The New Finis Z2 Swim Fins Youth does not overload the quads allowing a longer workout without the fatigue. Zoomers are the leading training fin used by competitive and fitness swimmers. The Z2 swim fin has more propulsion than the Original Zoomer. Also unlike a split fin the New Z2 differentiates between the upward kicking motion and the downward kicking motion. The fin is soft, due to the cutout on the bottom of the fin, on the downward motion allowing more propulsion and is stiff on the upward motion, due to the rails on the sides, for even greater propulsion.