most needed hole saws?

[kwirky]

anyone out there have suggestions for the "most nessesary" sizes for diamon hole saws? I'm looking to get a bunch off e-bay. All I know is the spears 3/4" tank adapter uses a 1-3/4" (45mm) hole saw. Other than that, I don't know what sizes to get. I wanna order them all at once to save on shipping (they'll be coming from china).

I'm thinking the most common piping used is 1/2", 3/4", 1", 1.5" and 2". so that's probably 4 hole saws in total. Can anyone tell me what sizes their tanks are drilled for, and the size of the holes cut?