Mac Allister Grip-Drive sockets offer the next generation in socket technology. Patented Advanced Cam Technology allows the socket to bite on to the sides of the bolt head even if its rounded, rusted, or otherwise damaged. The harder you turn, the tighter it grips! These tools also function as a bolt starter and will hold the bolt for easy installation in hard to reach areas (non-magnetic). Made of durable chrome vanadium steel it comes complete with a compact dual flip storage case.