Looks like the adapter is made for two sizes, see how it steps. Or you can fashion something out of an alum. rod or even hardwood dowel. Cut a section from a dowel of proper dia. and drill a center hole for the 'pin' of the tool to go in. I imagine you can fashion any size adapter you want.
For plumbing pipes, this pulls ONLY compression sleeves/ferrules for 1/2" OD; inner dia is smaller due to L or M sidewall thickness. By the way, to use as compression sleeve puller, UNSCREW the T-bar threaded bar from the "grab wing" (used to pull faucet knobs). Otherwise, the grab wings will get in the way of pulling compression sleeves/ferrules out.