Square Head Machine Bolts are available in diameters from #10-24 to 5/8". A few larger sizes may appear on the Odd Lots page. Choose your diameter from the following links:  #10 - 24  1/4" - 20  5/16" - 18  3/8" - 16  7/16" - 14  1/2" - 13  5/8" - 11 The chosen link will open in a new window. For Long and Custom-Length Square Head Machine Bolts, and Custom Cut and Threaded Stay Bolts, see our Long Bolts page.