Briley and DPMS are one piece.
Clark comes as two pieces, but you have to glue them together as part of the installation so they become a one piece when you are done.

In order to install one-piece handguards, you will want the DPMS freefloat tube wrench.
It reaches around the receiver from behind the handguard and has two pins that engage the holes in the barrel nut portion of the handguard.



Unfortunately, this wrench does NOT work with the DPMS low-pro receiver as that receiver is thicker than most others.
In that case, you are stuck with a strap wrench and my indexing shims to get it right.