This is a Rubber Long Barrel Grommet for car audio 1/0 cable, and it also fits my #FAM 4awg ofc cable as well.

These are rubber grommets, you may want to lube the wire up to make sure the wire slides through during install. They are flexible to help fit around the wire and give a flexible seal.

Outer Diameter: 1"
Inner Diameter: 0.63"
Height: 0.85"

This grommet DOES FIT my #FAM 4AWG OFC cable
This grommet DOES NOT FIT my #FAM 1/0 AWG OFC cable (grommet is too small)