You are buying on a 2" Heater Split Nut that measures about 2 7/8" inside the threads and about 2 1/4" on the inside part that touches the heater tube. The Heater Flange Split Nut mounts to the heater tube using 2 screws to hold it in place and screws onto the heater threaded union with a gasket between the union and tube. If your heater is 2"inside diameter this part is correct. This version is the most popular version. 1 1/2 x 1 1/2 is 2nd most popular and 1 1/2" X 2 is 3rd most popular.This part is used in hot tubs to plumb a heater tube to a heater union. We have plenty of these. Buy with caution I Do Not Accept returns!