Material: POLYESTER + latex silk Advantage: Great tensile strength, rebound flexibility is good, deep squat is the best action that increases the strength of the leg ministry, can still promote the strength of the system very well, the first selection that develops the muscle of the leg ministry , promotes muscle growth System, improves cardiac function. Get down to strengthen your heart. Practice squatting regularly to make your heart stronger. Size:Blue Lake: 76 * 8cm 30 ~ 40LBSPink: 76 * 8cm 50-60LBSPurple: 76 * 8cm 70-80LBS