Grip Heads are the strongest in the business! Set it and forget it...plates feature two holes of 3/8" and 5/8" diameter that eliminate any confusion. New castings offer positive lock in all directions. 2.5" size also comes in a millimeter version, new this year by Matthews. Mini Grip Head comes standard in MiniGrip Kit with 3/8" and 5/8" mounting holes. MICROGrip Head comes in new MICROGrip series of mounting products.