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.