This is an original Gib Hook off of an original Bobbin Case Assembly for a Singer Featherweight 221, 222K or Singer 301. Part number 45831 and 170160 are interchangeable, however, the front gib screw is not. Part 45831 requires a gib screw that has a sloped or angled head as it meets the shaft of the screw. Part 170160 requires a gib screw that has a 90 degree angle where the head meets the shaft.
The threads on both screws are the same, allowing either screw to screw in to the hook assembly. However, if the wrong screw is used, the screw will not be flush with the gib hook causing the thread to catch on it. (This could cause skipped stitches or thread jams.)
One last exception -- this gib hook will fit most all Featherweights. The only exception are the earliest edition hook assemblies (more info on the Featherweight Timeline). This older style gib hook can be easily identified by the gib screw hole -- if the gib screw hole is oval-shaped, then it is the very, very early style gib hook. If the gib screw hole is round, then the gib hook is the most common style and easily replaced. Feel free to contact us if you have any questions.