The On Stage SSA20M M20 Speaker Mount Adapter is a replacement adapter for your subwoofer mounting poles. The M20 threading has a much more solid hold than the original 1.375 inch sockets. This is meant to replace most of your sockets, just remove them and put these ones right in their place. M20 threading is the new standard for mounting poles. Give your setup the rock solid construction and wobble free connection with the subwoofer. Perfect to use with the On Stage Adjustable Subwoofer shaft. Includes 4 mounting screw.