Flat washers are used under bolt heads or nuts to increase the bearing area or offer greater hardness, so that the nut or bolt can be rotated without distortion of the bearing surface.

USS flat washers have a larger outer diameter than SAE flat washers.
Unit of Measure
Items
USS FLAT WASHER (USA), THRU HARDENED, PLAIN (INCH)

1/4 USS FLAT WASHER GRADE 8 DOMESTIC
Web Price $644.49

USS FLAT WASHER (USA), THRU HARDENED, PLAIN (INCH)

5/16 USS FLAT WASHER GRADE 8 DOMESTIC
Web Price $524.61

USS FLAT WASHER (USA), THRU HARDENED, PLAIN (INCH)

3/8 USS FLAT WASHER GRADE 8 DOMESTIC
Web Price $466.99

USS FLAT WASHER (USA), THRU HARDENED, PLAIN (INCH)

7/16 USS FLAT WASHER GRADE 8 DOMESTIC
Web Price $430.03

USS FLAT WASHER (USA), THRU HARDENED, PLAIN (INCH)

1/2 USS FLAT WASHER GRADE 8 DOMESTIC
Web Price $450.27
Diameter N/A 1/4 N/A 5/16 N/A 3/8 N/A 7/16 N/A 1/2
Length N/A
Material N/A Grade 8
Finish N/A Plain
Package Quantity N/A 6000 N/A 3500 N/A 2500 N/A 1500 N/A 1000