Screw mechanism for Swivel Stools

Replacement mechanism for most swivel-type piano stools.
Plate measures 4-1/2" x 4-1/2" with 4 screw holes on each plate.
There are 4 screw holes....one in each corner (they are 1/4" holes). These are spaced 3-3/8 apart (center to center)
Closed height at lowest 4" and opens up to 8"
O.D. of threaded tube is 1-1/4"