A flat washer with significantly more surface area than a USS or SAE washerThey are also made from a thinner gauge metal than most flat washersUsed where an extra wide bearing surface is required
Minerallac® Cully™ 70743J Fender Washer, 3/8 in ID x 1-1/4 in OD, 0.047 to 0.08 in THK, Stainless Steel