48" Speed Training Chute BlackResistance and overspeed 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 overs-peed 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 Advanced Under 170 lbs. S S, M M, L 170 to 210 lbs. S, M M, L XL Over 210 lbs. M, L L L & S, L & M