Versatile NBR Special Shape Seal Rings
https://www.zhejianghaiwei.com/product/oil-filter-seals/special-seal/

Versatile NBR Special Shape Seal Rings: their material and construction. Crafted from high-quality NBR (Nitrile Butadiene Rubber), this gasket ensures durability, resilience, and good resistance to oils, fuels, and other fluids.