UNF DOME NUTS A2 STAINLESS STEEL HEX ACORN 10 1/4" 5/16" 3/8" 1/2" 5/8" 1/2"

1/4"UNF - 28tpi; across the flats 0.437"; overall height 0.468". 5/16"UNF - 24tpi; across the flats 0.562"; overall height 0.531". 3/8"UNF - 24tpi; across the flats 0.625"; overall height 0.625". 1/2"UNF - 20tpi; across the flats 0.750"; overall height 0.812".

eBay