compact green laser sight in black alloy casing which is shock and water proof. Complete with dual size barrel mount OR dual fit rail mount. Battery charger also included. 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. 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 batter charger. + I have 222 Loctite listed and its recommended to use on the screws.