Why do plumbing washers have letters and numbers on them?

20 Volt Cordless 4-in-1 18-Gauge 2″ Flooring Nailer, 57% OFF

20 Volt Cordless 4-in-1 18-Gauge 2″ Flooring Nailer, 57% OFF

DANCO 5/8 in. Flat Faucet Washers (10-Pack) 88574 - The Home Depot

20 Volt Cordless 4-in-1 18-Gauge 2″ Flooring Nailer, 57% OFF

DANCO 5/8 in. Flat Faucet Washers (10-Pack) 88574 - The Home Depot

20 Volt Cordless 4-in-1 18-Gauge 2″ Flooring Nailer, 57% OFF

american standard 3 handle shower, balancing C/H water

DANCO 5/8 in. Flat Faucet Washers (10-Pack) 88574 - The Home Depot

20 Volt Cordless 4-in-1 18-Gauge 2″ Flooring Nailer, 57% OFF

20 Volt Cordless 4-in-1 18-Gauge 2″ Flooring Nailer, 57% OFF