The bracket rail adapter is the center rail of the ARC OPS helmet, which is suitable for most FAST series helmets, ACH series helmets and MICH helmets. 360° free rotation, the rail bracket can be fixed on the helmet top rail and both sides of the helmet rail, the center telescopic rod can be adjusted freely. The ear cups are made of silicone, which is more comfortable to wear and can bring better wearing experience compared with sponge ear cups. Headphone plug: military standard 7.0 mm plug. The plug wire is made of kraft paper wire and TEP cover. It has flexibility, strength and frost resistance, and is not easy to be hardened by aging. These headphones use electronic active noise cancellation and sound capture technology to provide clearer and more natural sound and protection for your ears. Please press the “+” and “-” buttons at the same time to turn on the headphones (do not hold down the “+” or “-” buttons, press and hold them at the same time for at least 3 seconds). Note :This product does not include battery and helmet.