These are the official SOCOM-issue Armorer’s Block Set for the FNH SCAR MK16 & MK17. All major service procedures for this weapon system can be accomplished easily using the 5 piece set. Allows barrel service, trigger module repair, and bolt disassembly/reassembly for both calibers. Mounts MK13 grenade launcher for inspection and service as well. High grade injection molded nylon prevents marking or marring of weapon. For professional armorer or gunsmith use only.