I have found that commonly available washers just don't cut it for holding a shifter in place. Those commonly used are too small in diameter and close to falling in the wide slots of the shifter holes, this can't provide good clamping force on the shifter. Fender washer are just too big, and restrict adjustment. These are a thick washer with the perfect not too small not too big diameter. Button head bolts provide the most under head surface area this combine with the washers provides a shifter that stays in adjustment.
Bolts are included, and correct size can be supplied to meet your needs, I realize not all shifter flanges are the same thickness, example Berg rapid travel shifters have a crazy thick flange and I can provide the needed bolts...........Joe
As always made in the USA