I have Buttonhole Attachment No. 86662, which is practically identical to the 121795, except the black casing is shaped slightly different and there is a tiny finger that holds the material down when stitching. You can take the black lid off, disasseble it entirely but often you don't need to. Mine was fairly clean, very dry and hardly trace of oil at all, and after superficial cleaning and oiling it clicked a long fine on the machine. This is the attachment I like the best, it works well and is very useful.