This strap improves mask stability and helps prevent leaks. It attaches over the hose connection, wraps around your head, and secures with velcro on the side. The strap can be shortened by cutting between the two velcro pieces at one end. It’s compatible with the Mirage Quattro and other full-face masks and comes in two sizes: Regular (31 inches) and Long (33 inches), both adjustable if needed. The Anti-Leak Strap is for the following masks and may work on others as well: ResMed Mirage Quattro ResMed Quattro FX Philips Respironics Comfort Gel Full Philips Respironics Amara Fisher Paykel Simplus Fisher Paykel Vitera Do not use on the following masks: ResMed Quattro Air ResMed AirFit F10 ResMed AirFit F20 (there is an Anti-Leak Strap just for this mask) ResMed Mirage FX Machine washing and drying is not recommended as this will make your strap shrink, but there are other ways to care for it. To get a nice scent on your new microfiber sleep mask without risking the shrinking issue (and also to help remove any excess dye), we recommend hand-washing in warm soapy water followed by a good rinse with cool or cold water afterward.