blevblev @skyler_kopkoI I agree - the "key" that fits into the opening at the end of the spool - in every case I see in roll film cameras - is a cylindrical opening, with wings or extensions on either side - like in Skyler's photo. I had to set with a knife an drill a hole in the middle of the slot to get it to engage. The other thing is that it shouldn't have a straight edge, but it should have a curved shoulder on the end. That would prevent the whole works from binding down from friction especially when you get to the end of a roll. The purpose of this should be simply to make the spool longer, it doesn't have to have sharp edges.