Hank, that can be a difficult question… I understand why you ask though….bushings are expensive…..if your working on clocks there can be a large range of sizes…I am just guessing without having your clock in hand so my best advice is to go ahead and take it apart, measure the pivot sizes, plate thickness and order what you need or a set with those sizes included…if you want a quick answer and are intending on buying sets of bushing for the future for the average American time and strike clock movements I would be in the mid range….from pivot size 1.00mm to 1.75mm plate thickness possibly from 1.50mm to 2.00 mm….and these may not be all that would be needed, you have the center wheel arbor, great wheel arbors and different styles and configurations of movements to consider.