I have a home made newtonian telescope with a Moonlite focuser. I like to leave the coma corrector inside the focuser, and so needed a dust cap to protect it. The dustup goes inside the telescope tube.
This dustcap has an inside diameter of 2.25" and fits the exterior of the draw tube of the Moonlite CR 2 inch Newtonian focuser.
At 100% fit was bit tight, so you may want to print a little larger, say 102%.