These balls are the most durable on the market. Tested to over 3000lbs of pressure.  Slam balls can be added to a variety of exercises simply by holding the ball while performing the exercise.  Some examples are squats, sit-ups, overhead presses and lunges.  Slam balls also work for partner exercises such as chest passes, overhead passes and rotational abdominal work where partners stand back to back and twist to pass the ball to each other.  Slam balls can be used for standard weight-lifting exercises in place of free weights and for dynamic exercises that involve an increased cardiovascular aspect.  Slam balls are also effective for athletic training because they improve muscle mass, cardiovascular endurance and hand-eye coordination.