Remove the earmuffs on the two sides of the earphone from the stand. Take out the wire of headphones. Buckle the earmuff on the hanging buckle of this rail adapter (corresponding location, both left and right). Wire the headset on the of the helmet according to your own situation, then fix it on the of the helmet. Features - Color: Black. - Material: Alloy, nylon. - Size: About 15x9x4.5cm - Suitable for 19-21mm helmet guide rail. - Remove the earmuffs on the two sides of the earphone from the stand - Take out the wire of headphones - Buckle the earmuff on the hanging buckle of this rail adapter (corresponding location, both left and right) - Wire the headset on the of the helmet according to your own situation, then fix it on the of the helmet Package list: 1 x Set of Helmet Rail