This item is a 3 5/8" wide 6 Spoke Watefall or Neck Jet Control Diverter Knob, Diverter Cap and O-ring Kit for a 1" Waterfall or Neck Jet Control..
The inside thread measurement is about 1 5/8" and the center hole is about 3/4"..
It uses (2) Small o-rings and one O-Ring Gasket that measures about 1 1/2" center to center..
