Uncle Mike s pioneered the modern swivel in 1947 and has continued to make the strongest most reliable swivels on the market. Any other brand is a weak link between you and your firearm. Swivel Lock is a spring loaded plunger and a knurled threaded sleeve that locks down to completely eliminate accidental opening of the swivel. Uncle Mike s swivels are positively secured for the long haul. Closed Link technology creates a permanent ring bond that will never fail you. It was the first of its kind and started the entire generation of Uncle Mike s QD Swivels. 1/2-inch deep-threaded wood screw and fore-end base. Swivel Lock spring-loaded plunger and a knurled threaded sleeve eliminates accidental opening of the swivel. Closed Link technology creates a permanent ring bond.