Amazon.com: Watch Back rubber, 31 mm-40 mm Watch O-ring seal Watch Back Sealing rubber spare parts, replacement of the O-ring seal (0.7 mm + 0.8 mm + 0.9 mm) : Clothing, Shoes & Jewelry
MECCANIXITY Fluorine Rubber O-Rings 40mm 44mm OD 33mm 37mm ID 3.5mm Thick, FKM Sealing Gaskets for Plumbing Pneumatic Repair, Green 2in 1 Set - - Amazon.com