Anti-squeak stuff. It's a rubber U-shape that fits over the edge of the inner fenders to fill the gaps.
Jim Carter has it available as a package for both the inner-to-outer fenders and inner fender to cab anti-squeak (which is just tar-paper). Their PN FP119.
[on edit] I spent too much time hunting the part number down. Dan got there before me.
Last edited by klhansen; 09/23/2024 1:34 AM.