Twist Lock for slot style racks
This model is designed to drop into 1/2 inch slot style racks. Some racks instead of holes have long slits for cramming frag plugs closer together. This is made for that type of rack so the frag can only be removed by the rotating and pulling in the correct order. Not a snug fit, like some other adapters, but will prevent your frags from coming out of the rack on their own.