On the right side is the under side of the casette and the arrow indicates the hole that must be widened a little
Since many years I have not found original ribbon bands to my dotmatrix printer Panasonic KX-P2023 from 1996.
From Stinkyink.com, U.K I bought generic Panasonic bands KX-P115i and they worked very well.
However, when I needed new bands I ordered original Panasonic bands KX-P115i (Made in Vietnam) from swedish www.123ink.se actually cheaper than from Stinkyink.com. However, these band did not fit and I read that others complained over it too. When I studied it I found that on the right side on the printer there is a peg and the hole in the ribbon cassette did not fit with it.
I took my Swiss Army knife smallest blade and widened the hole (see picture) a little and then suddenly the print cassette fitted and snapped in place.
Hurray my old printer was saved!
A dot matrix printer gives permanent text, which is an advantage and is cheaper than a laser printer.