The ACU-X Snap-On Lighted Nock contains a one-piece Nock/LED unit that is indexed with the vanes and press fits into the arrow s Aluminum Bushing. Upon firing the crossbow, the bowstring s force compresses the two pieces and activates the lighted nock. Deactivate the easy on/off ACU-X Snap-On Lighted Nock by pulling the nock straight out until the light turns off. Use of the Bednar Perfect Puller 2.0 makes lighted nock deactivation extremely easy. Product Features Easy-to-use one-piece ACU-X Snap-On Nock / LED unit no assembly required 515+ FPS approved Features a Nock Retention Groove that allows the user to both hear and feel the positive engagement of the nock to the string on TenPoint rail-less crossbows Bowstring activated Super bright LED light provides superior arrow flight visibility Easy deactivation 24-hour battery life when activated (approximate) Features TenPoint s ACU-X Snap-On Nock (Only for use with TenPoint Rail-Less Crossbows) Fits all TenPoint & Wicked Ridge arrows with an HP Aluminum Bushing (sold separately)