The Dunlop strap ring is made out of plastic and works with stringed instruments that fix themselves on the strap with a pin. The strap ring is made out of plastic and has a Dunlop logo on the back. The way you attach it to the pin is by rotating the plastic piece in the locking ring. By rotating the inside ring you are able to adjust the size of the hole that the pin goes into. Once there you can rotate back to fix the strap ring lock. The ring lock works well, even if I wouldn't advice you to lay the instrument down on the strap lock, because it is made out of plastic and is not all that durable or powerful. The ring has lasted well ever since I bought it, but that was not a very long time ago. The thing is that most straps are too thick and the pin is to short in general. There is a lot of pressure on the ring, but it is better than a rubber ring that would slip off. The ultimate choice would however mounting fixed strap locks in the place of the pins. The Dunlop pin lock is great for all instruments that have pins to ensure that it doesn't fall off while you are standing and adds more lifetime to your used straps.