This shows the problem i encountered when trying to use a standard 66mm ventolin inhaler with the http://www.thingiverse.com/thing:1454425. the picture with one arrow shows that the canister nozzle cannot go any further down so the canister just balances in the chamber, although the mist does spray out properly when pressed down. the second picture with 2 arrows shows the bottom arrow demonstrating that the cap cannot go down any further (due to the height of the canister) so it can't close and lock. the upper arrow shows where the canister is too tall and the cap is resting on the top of the canister and can go down no further, also preventing it from closing.