The 81 Series includes three models and can accommodate over 30 Atlas Sound baffles. The 81-8S is designed to mount 8" loudspeakers and has a square cut-out with a multi-position hole pattern to accommodate an extensive variety of round and square baffles including torsion spring and screw mount models. (See chart below for specific baffle model numbers.) Adaptability of the 81-8S also makes it ideal as a stocking item. Model 81-4 features a round cut-out and accepts 4" loudspeaker baffle Models 51-4 and 60-4. Model 81-8R, like the 81-8S, handles 8" loudspeakers but features a round cut-out that suits baffles mounting the industry standard Atlas Sound 95 Series enclosures. All tile bridges are constructed of 24-gauge CRS with an electrogalvanized rust-resistant finish. Features Load-Bearing Bridges Eliminate Ceiling Tile Sag by Distributing Assembly Weight to Ceiling's Support System Round cut-out that suits baffles mounting the industry standard Atlas Sound 95 Series enclosures Rust-Resistant 24-Gauge Electrogalvanized Steel Construction Ensures Long Service Life Applications Utilize Atlas Sound 81 Series tile bridges to prevent ceiling tile sag in suspended ceiling installations of loudspeaker assemblies. The 81-8S and 81-8R (accepting 8" loudspeakers) and the 81-4 (designed for 4" loudspeakers) distribute the assembly weight to overhead T-Bar support members