-Fits dovetail 11mm rail.-Dovetail rail extension.-Can be used to convert 11mm to 20mm.Specification:Top Rail Full Length: 100mmDove rail length: 75mmTop Picatinny rail width: 20mmBottom dovetail rail width: 11mmWeight: 80gMaterial: aluminum alloyColor: BlackPackage included:1 x Rail Base Adapter1 x Allen Wrench