This nylon-polymer handguard set fits almost anywhere a carbine-length drop-in system is needed. It comes in two parts, and fits the KM4 Commando, CQR Series, KM4A1, and KM4 CQB. It also fits as a replacement set for the original PTS RM4 Series, but also fits on the new RM4A1. On the RM4 and KM4 diagrams, these parts will appear as 257 and 258.