O-Rings and Seals

Danco rubber O-rings in the standard plumbing sizes, listed by outside and inside diameter and by the conventional number — #7 at 1/2 x 3/8 in. through #49 at 1-7/8 x 1-5/8 in. An O-ring is specified by inside diameter and cross section, and the cross section is what actually seals; two rings with the same ID and different thickness are not substitutes. Stretch the ring more than a little to fit and it thins and leaks. These are the faucet, valve stem and spout O-rings for common repair work, so the practical approach is to bring the old ring or the stem to size it rather than measuring a ring that has already swelled in service.