These risers are 100% solid Aluminum. They secure tightly to a standard picatinny rail. Will not be disappointed with the quality of these risers.1. Constructed by aluminum alloy in andoized matte black finish.2. Quick release Thumb tightening system，Mounts to a common 20mm rail system.4.Fits AR series/M series and the other Flat Tops.5. See Through design allows the users to see the iron sights when mounted.Specifications:- Length:85mm(3.35")，High:13mm- Weight: 70g- Rise: 1/2 half Inch"- Material: Aluminum alloy