The Rhineland Arms SD-15 handguard system is designed from the ground up with modularity in mind. The primary handguard is in the design of the famous Mp5-SD handguard but with the added benefit of having a rail on top and adding another on the bottom. Both ends are threaded for mounting to the rifle as well as threading fake suppressor bodies into the end. Constructed of thick wall 6061 aluminum and 5″ long. This is to be used with any length barrel from 3″ to 16.5″. These come with the mounting wrench and will fit all AR15 upper receivers and work with any blowback configuration. The inner diameter of the handguard is 1.51″ and you will want to use a flash can for barrels under 8″. Standard picatinny rail included for the top.