If you"re craving an ADVANCED LEVEL of gyroscopic fitness, the Iron Power Force One Gyro is what you have been looking for. It utilizes German precision engineering to create up to 16,000 rpm and 50 pounds of silky-smooth dynamic resistance in the palm of your hand. Describing the Iron Power experience is challenging at best, because you have never felt anything like it before. But imagine a sphere the approximate size of a tennis ball that feels as though you are lifting a 50 pound dumbbell when spinning at full speed. The faster the Iron Power Force One Gyro spins, the more resistance is automatically added. This exerciser is perfect for the experienced Powerballer, Mixed Martial Artist or extreme athlete looking for a challenge or a way to get a competitive edge in their sport of choice. THE DYNAFLEX IRON POWER LINE IS RECOMMENDED FOR EXPERIENCED USERS ONLY! If you"re a beginning Powerball user, we recommend you begin with the entry-level plastic Powerballs or this Iron Power gyroscope will only end up being a heavy paperweight on your desk.