compact red laser sight in black alloy casing which is shock and water proof. Complete with optional dual size barrel mount or dual fit rail mount and a pressure pad tail on switch. 1) Barrel Mounted Package includes: Green laser sight <5mw Length 80mm. Barrel mount. Fit barrels 10mm to 23mm wide (different size each side). allen keys. windage & elevation adjustment. Push button on / off. Rechargeable LS 14250 battery. USB battery charger. On / Off pressure tail switch. 2) Rail Mounted Package includes: Green laser sight <1mw Length 80mm. Dual fit rail mount. Fits on Dovetail and Picatinny / Weaver rails. allen keys. Push button on / off. Rechargeable LS 14250 battery. USB battery charger. On / Off pressure tail switch. + I have 222 Loctite listed and its recommended to use on the screws.