sized housing cap for bathtub faucet

to repair leaky bathtub faucet I had to unscrew plastic handle and then open central housing cap. screw on the faucet after spray of wd40 gave up quite easily, but the chrome big housing wouldn't move. knocking, heating with heat gun, using vice grip or channel lock would not loosen it. multiple wd40 spraying also wouldn't work. finally soaking it with wd40 and leaving overnight helped. wd40 penetrated the thread and after using vice grip and slight tapping with hammer, it started to move. instead of replacing the whole unit, two seals and springs fixed the leak. total cost $6.50 for parts and about 1/4 of the wd40 can, saved a lot of money replacing the whole bathtub faucet.