The LBS4-DX is designed specifically to mount 4” (EIA 5”) speakers with torsion or screw mount grilles to backbox models DX104T, DX104 and CP4 as noted. The LBS4-series is engineered to distribute the speaker assembly weight to the ceiling support system in a suspended 2' x 2' or 2' x 4' tile ceiling system. It is galvanized 20-gauge steel (23.75"L x 12.125"W) with a round center opening.