I only tried it on after opening it; it's a gift. I don't use eye masks, so I'm offering it to someone who needs it. The main unit only. Thank you very much! ^_^ Blocks light stimulation that disturbs sleep. A lightweight eye mask that fits without feeling tight. 3D Sleep Eye Mask MYTREX Eye Air A sleep eye mask that focuses on "light blocking," "fit," and "texture," which are essential for eye masks. It gently wraps around your eyes with a unique 3D structure and low-resilience cushioning to block out light effectively. You can adjust the size with the Velcro (magic tape) to achieve your preferred fit.