Mounting Bracket for Mounting Speaker Cabinets on Speaker Stands - 1-3/8. What do you do if you have a speaker cabinet that does not have a built-in speaker mount socket, but you'd like to use it on top of a tripod speaker stand? Simply install a TSM-138MK to the bottom of the speaker cabinet, and you're set! The TSM-138MK is an internal, metal mounting bracket for speaker cabinets that do not have built-in speaker mount sockets. It mounts on the bottom of a speaker cabinet (mounting inside the speaker cabinet) with included installation hardware.SpecsInternal metal bracket securely mounts any speaker cabinet with a flat bottom.Fits 1-3/8" (35 mm) tubeDiameter is 4" (102 mm)Metal fitting holds 138 lbs. (68.2 kg)