Adapt an M20 speaker stand shaft to connect to virtually any subwoofer mounting socket with our SSA21 Subwoofer Adapter. To increase speaker mount compatibility, this adapter features a 1 3/8" mounting pole with a removable M20-threaded lug that enables a proper fit for virtually any socket including shallow M20, recessed M20, 1 3/8" cup, and 1 3/8" cup with M20. Its heavy-duty construction ensures sturdy support for reliable speaker placement.