Cap Diameter of 100mm. Common diverter parts for many older spas. This is the Non-Buttress style that suited Monarch and many other brands in the late 1990s and early 2000s. Very common on Monarch Spas. These have a V-shaped thread on the body. If you have a Buttress-threaded diverter, you will need parts for a different (Waterway) diverter.
Important Notes: There are similar parts to these. In order for these to fit, your Cap must *not* have the word "Buttress" printed underneath. If it does say "Buttress" use the parts listed here. See below photo to double-check the thread on your diverter body.
"Buttress" is a later type of thread used. Non-Buttress "V-Shape" thread is used on older spas.