The NiimBot D101 is a great label printer, and has the ability to print ½" and 1" wide labels. To handle the different sized labels there is a little piece of very specifically shaped plastic that slots inside to keep the smaller labels in the correct place. It's big flaw is that there is no way to hold the little piece of plastic if you are not using it. So ultimately it gets put somewhere safe and then you forget where that is!

UPDATE: I found the original, so rather than being a functional guess, this model is now a copy of the original and clicks into place exactly.