Automatic lighting: illuminated nock is designed with a switch button, when bowstring is operated, switch will be activated, and nock will automatically when material: automatic hunting nock is made plastic material, which is strong and durable, not easy to break and deform Easy to use: bow requires no assembly steps, just insert nock into shaft, aim where you want, and you're ready to Suitable Size: LED nocks fit into shafts with an inner diameter 0.244inch (6.2mm). Please check carefully before purchasing High Visibility: Clear plastic for maximum light transmission, find arrows even at night or at dawn Material: plastic colour: red(after power on) Package Contents: 6 x LED Lighted Nock Tail (red light) 2 x screwdrivers Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.