M83248 series o-rings are flurocarbon rubber o-rings. Flurocarbon rubber is commonly known as Viton. It is an advanced rubber that has extremely good fuel and heat resistance and is ideally suited for aircraft fuel system applications.
Excellent resistance to acids, fuels, mineral and vegetable oils and greases, aliphatic, aromatic and chlorinated hydrocarbons, non-flammable hydraulic fluids (HFD) and many organic solvents and chemicals. Low swelling in ASTM oil No. 1, and IRM 902 and IRM 903
These are so hard to find, Vans does not sell them, so your the best source. Problem is your cross reference makes it hard to find for your sales person! I almost gave up.