My 5er is currently not at home but the last time I towed it I noticed my lube plate is pretty much done. I need to order a new one but notice there's a 10" and 12" plate. I didn't measure my current ...
The size of the lube plate is based off your hitch. You can get the correct size for the plate off your hitch brand. I never saw a big deal in the size of them though, maybe it is important.