Singer sewing machine stop motion knob lock washer, part #2020. Compatible with the #256 stop motion knob that is found on the model 15 (excluding the 15-91), 66, 99, 115, 127, 128, 201-3 / 201K (excluding the 201-2), 306, 319, etc. Good vintage condition, clean and rust free. Original, genuine Simanco part. *Please note that this washer is not compatible with the Featherweight.