Brand: Automotive Racing Products (ARP)
These hardened, parallel-ground ARP chrome moly washers are ideal for distributing a clamp load over a larger area than standard washers.   
These 3/8" ID washers have an oversized 0.675" OD that is la little arger than the 0.625" OD of AN960-618 washers but much smaller than the 1 5/8" OD of AN970-6 washers.  Extra-thick 0.120" thickness is almost like stacking 2 AN960-616 washers.  Black oxide finish.  Sold in packs of 10. 
 | 3/8" Washer Comparison | 
 | Washer | OD | Thickness | 
 | AN960-616 | 0.625" | 0.063" | 
 | ARP200-8556 | 0.675" | 0.120" | 
 | AN970-6 | 1.625" | 0.063" |