CA gas tank sending unit O-rings are a small and very inexpensive part, but they play a key role in your sending unit assembly. These rubber gaskets help to seal out contaminants and protect the unit—so that accurate fuel level data can be relayed to your dashboard fuel gauge. Submerged in gasoline, your original O-rings can show signs of wear, especially after many decades of use. Order the replacement O-rings recommended for your application.