1Used for Fast helmets or other modified helmet equipment guide rail. 2Including screws and nuts, it is easy to install onto helmet. 3With it ,you can attach lights, lasers, cameras or other devices to helmet by using standard arc rail dovetail adapter(not included). 4It can be firmly fixed on your helmet, not easy to drop. 5Nice accessory for your combat helmet, providing much convenience.Features: Used for Fast helmets or other modified helmet equipment guide rail. Including screws and nuts, it is easy to install onto helmet. With it ,you can attach lights, lasers, cameras or other devices to helmet by using standard arc rail dovetail adapter(not included). It can be firmly fixed on your helmet, not easy to drop. Nice accessory for your combat helmet, providing much convenience. Specification: Condition: 100% Brand New Material: ABS Color: Black, Green, Mud Color(Optional) Single Rail Size(L * W): Approx. 19 * 6.3cm / 7.5 * 2.5in Weight: Approx. 129 - 142g Packing List: 1 x Pair of Rails 4 x Screws 4 x Nuts Note:Please note that the new type and old type of this product will be sent randomly, and make sure you will not mind before ordering.