Everbilt 3-1/2 in. x 3-1/4 in. x 1/8 in. Buna Rubber O-Ring 837488 - The Home Depot
PROSEALS USA provides o-rings and engineered sealing products, including PTFE, rubber o-rings, metal o-rings, Precix, Trelleborg, Parco, metal seals, and sealing products for critical applications and industrial customers such as automotive, oil
O-ring - Wikipedia
O-Rings
Captain O-Ring - K4 Replacement O-Ring Kit for OmniFilter K4, CBF1, CBF3, SFM2, U30, USM2, OT32, RO2000, RO2050, and More (2 Sets, 8 Orings): Amazon.com: Tools & Home Improvement
Rubber O Rings: Types, Rubbers, Benefits, and Design
Installing, Replacing, and Measuring O-rings | Tameson.com