Ring, stretch, silver-finished brass and "pewter" (zinc-based alloy), 8mm wide with 20mm perforated disk, size 6-1/2 to 8. Sold individually. - Fire Mountain Gems and Beads
10x Oil Drain Plug Crush Washer Gaskets For Subaru Ring Size 25mm Open Size 20mm | eBay
UK / US / EU Ring Size Chart / Downloadable Ring Size Chart / - Etsy
uxcell Nitrile Rubber O-Rings 20mm OD 10mm ID 5mm Width, Metric Sealing Gasket for Automotive Machine Plumbing, Pack of 10: Amazon.com: Tools & Home Improvement