Check the listing for details. Hot Tub Spa 2" Heater or Pump Union Gasket Combo (1) 2 1/2" Lip & (1) 2 5/8" Lip. Condition: New. Listed at 8.99 USD. This Kit is a Combination of the Two Standard Size 2" Heater or Pump Union Gasket (1) with a 2 1/2" Lip Center to Center and (1) with a 2 5/8" Lip Center To Center. Note: Make sure you have 2" unions that measure 3" across the threads.. Look in the picture section for measurement examples of the unions these fit.. The purpose of this Combo Kit is if you don't know which size you have you get both.. Use One and throw the other away.. Gasket #1: The gasket is 2 7/8" across on the outside the inside diameter is about 2 3/16" and the lip that fits into the union is 2 1/2" center to center and fits most unions but there a few exceptions so please measure. If you order this gasket and the ridge doesn't fit you union you can trim the ridge off and use it as a flat gasket. Gasket #2: The gasket is 2 7/8" across on the outside the inside diameter is about 2" and the lip that fits into the union is 2 5/8" center to center and fits some unions but most unions are 2 1/2" center to center..This Kit is a Combination of the Two Standard Size 2" Heater or Pump Union Gasket (1) with a 2 1/2" Lip Center to Center and (1) with a 2 5/8" Lip Center To Center. Note: Make sure you have 2" unions that measure 3" across the threads.. Look in the picture section for measurement examples of the unions these fit.. The purpose of this Combo Kit is if you don't know which size you have you get both.. Use One and throw the other away.. Gasket #1: The gasket is 2 7/8" across on the outside the inside diameter is about 2 3/16" and the lip that fits into the union is 2 1/2" center to center and fits most unions but there a few exceptions so please measure. If you order this gasket and the ridge doesn't fit you union you can trim the ridge off and use it as a flat gasket. Gasket #2: The gasket is 2 7/8" across on the outside the inside diameter is about 2" and the lip that fits into the union is 2 5/8" center to center and fits some unions but most unions are 2 1/2" center to center..