Nu-Hope Barrier Washer 1-3/8" Opening, 2-1/2" OD, 1/2" W, Standard Like a second skin, Nu-Hope Barrier was developed of special materials designed to provide the most comfortable skin protection and seal available. Flexible, durable, and affordable. A washer's outside diameter is relative to it's hole diameter. The wall on all washers is 1/2" in width.