The rail adapter is designed to rotate 360° and so you can easily get your headphones out the way if you need to. The hole on the top of the claw is a square hole, and the telescopic column has a groove. Then insert it into the square hole, and rotate 90° to fasten. Note that groove of iron line is the key to fasten plastic circle. Take out the original accessories with both fingers, install the bracket accessories, and finally slide into the helmet. The right position of raised part with rail is up and if is down mounts will not press the earmuffs onto ears and this will be hard enough to seal. Suitable for ARC rails.