Hand Strengtheners Exercise & Fitness, Relentless Strength, Sports & Fitness, Sports & Outdoors, Strength Training Equipment Sphere Grip Hook Review by BrokenBoy May 27, 2018 No Comments They are designed to hold up to your toughest challenge and strong enough to pull a truck. Improve your grip strength by implementing these hooks into your pull ups, sled pulls, or hook them into kettle bells for a different spin on grip training