It is sold in both 3 and 4 prong version. You will have to specify at the store when purchasing. There was some confusion at the store as to which one I would need. Was given the four prong but as expected, the one in my home was a three prong so had to go back and return the four prong. The information that was given to me by the sales staff is generally speaking, the four prong versions are normally used in newer homes built after 2000. Hope this helps.