Uncle Mike pioneered the modern swivel in 1947 and went on to make the strongest and most reliable swivels on the market. Any other mark is a weak link between you and your firearm. The swivel lock is a spring-loaded plunger and knurled threaded sleeve that locks to completely eliminate accidental swivel opening. Uncle Mike swivels are fixed positively for the long haul. Closed Link technology creates a permanent ring link that you will never miss. It was the first of its kind and started the entire generation of Uncle Mike's QD swivels.