This strap is designed to add stability to the mask and prevent leaks. The strap attaches to the mask over the hose connection and then wraps around your head and connects with velcro on the side. There are 2 pieces of velcro at one end, you can cut between these to shorten the strap if necessary. There is a black strip covering over a central piece of velcro that you can remove if you want to attach it to your headgear. It was designed for the Mirage Quattro but will work on several full face masks. This is available in 2 sizes. The regular length is 31 inches and the Long is 33 inches. You can shorten either one of these by cutting between the velcro, if necessary.