Size of prethreaded holes on underside of rocker panel for 3rd gen?

I am still waiting for my 2021 Off Road to arrive, but in the meantime I ordered some step rails that has brackets that just screw into the prethreaded holes underneath the truck on the rocker panel (and yes, I know, should have gotten real RCI sliders, but couldn't bring myself to spend that much since I have no intention of going rock crawling in this anytime soon, ha!). That said, I want to order some rubber washers to prevent the metal on metal contact from the brackets on the underside of the truck (to prevent any possible eventual rust), but I am not sure what size those holes are. Any 3rd gen folks know? I searched other threads but only found sizes for the holes under the hood for mounting a compressor, and on the cab for mounting a roof rack, but haven't seen this info anywhere. Thanks in advance!

 

Perfect!!! thank you!!!!