Use the principle of parachute assisted reverse aerodynamics to build blazing sprint speed! As used by top pro football teams and world class sprinters. The Speed Parachute combines resistance and over-speed running during the run - the two key elements of speed training. The Speed Parachute provides resistance in the initial part of the run. During the run, release the Speed Parachute to initiate the over-speed phase. Feel the "shot out of a cannon" exhilaration! This combination increases your speed, explosiveness, acceleration, and stamina while improving running technique.Below is a basic guide for selecting the proper chute. This is a basic guideline and every athlete is different.Small Workout Parachute - 40" x 40"Medium Speed Training Parachutes for Running - 48" x 48"Large Sprint Training Parachute for Runners - 56" x 56"Small 15 lbs. Running Parachute Resistance* 40" x 40"Medium Speed Chutes 20 lbs. resistance * 48" x 48"Large Run Parachutes 30 lbs. resistance * Runner Parachute 56" x 56"Athlete"s Weight Beginner Intermediate AdvancedUnder 170 lbs. S S, M M, L170 to 210 lbs. S, M M, L XLOver 210 lbs. M, L L L & S, L & M