You are buying a 1 1/2" Spigot X 1 1/2" Slip Slice Gate Valve and 1 1/2" Heater Union with Gasket or Oring that matches the Union. The Valve recieves a 1 1/2" pipe or fitting on one side and then slips inside of a 1 1/2" fitting on the other side. It will slip inside of the Heater union and glue and screw to a 1 1/2" Heater Flange fitting. This setup is usually found in a hot tub that is 115v Plug in only. Measure the Heater flange and be sure it is about 2 3/8 across the end of the heater tube flange. Don't be confused we also offer a slice valve with a Pump union look at where it it attached in the spa if it is attached to the Heater and the plumbing is 1 1/2" and the Heater Split Nut threads are 1 1/2" then this part is correct. This part is used in hot tubs to stop the water so you could service the heater or the pump without draining the tub. Note: We do offer this Valve and union individually and in a set of (2) in our store. We have done a lot of extra work with videos and pictures to prevent you from choosing the wrong part. For help please find our YouTube video "1 1/2" Hot Tub Heater Union & 1 1/2" Slice Valve Kit How To Video American Spa Parts".