You are buying a 2" Heater Split Nut which includes the split nut and (2) Screws for use with a 2" Heater Union which would measure about 3" Edge to edge on the threads this split nut screws on. 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. If your plumbing is 2" and your heater is 2" 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. See our store as this split nut is also available in a kit with the related gasket. Note: The Heater tube in pictures is NOT included!!