8" Type B Gas Vent Square Firestop Support Square 8GVRS This firestop support is used to support vent at ceiling level. Includes clamp that supports and prevents pipe sections from slipping down. Provides the mandatory 1" clearance to combustibles. Straps extend 16". For Category 1 gas appliances 1" clearance to combustibles Easy-fit twist-lock design with no fitting hassles 0.012" aluminum inner 0.018" galvanized outer .010†Double-wall aluminum flex inner wall (two-ply .005â€) .018†galvalume outer wall with twist-lock connections.