Retainer attaches to the back rim of your hard-hat and loops over the front. It secures your goggles to your hard-hat. Elastic bands attach to the goggles to allow you to move them down onto your face while the retainer is still on the hard-hat. Small fits cap style helmets and large fits full brim helmets. Replacement elastic cords are sold separately in packs of 10, to refurbish your old retainers.