The Heavy Grips" hand gripper series was developed for athletes who want to take the training of their grip strength to the next level. These high-quality aluminum-handled handgrippers are made in 50lb increments from 100lbs to 300lbs * so that you can train your grip similar to training any other bodypart-- by increasing resistance. *Grip strength is approximate and does not compare to strengths of any other grippers on the market. If you want to develop serious hand strength for a sport, or just want to impress your friends, than the Heavy Grips" hand grippers is the only choice for you!