I have a Blue Ox base plate and tow bar. As you are aware the connectors on the tow car twist in and out. When they are out is there a plug or cover for this round hole as they seem to rust inside and become very noticable. Tks DAN
No plug that I am aware of. I just spray the hole with corrosion-X and no rust.
New Blue Ox baseplates come with plastic plugs that do not fit very tight and seem to be for shipping only. Our baseplate also needs paint from time to time. Maybe Blue Ox will send you a pair of those plastic plugs.
A friend used a plumbing part, from a hardware store.
Label on the cap per the photo he sent me last night, says "Pipeconx by Uniseal 1 1/2" size, made in USA, Evensville Indiana, Plastic or Cast Iron"
PIPECONX - Universal Pipe Connectors (http://www.pipeconx.com/cap_ec.php)
Note that the part comes with a band clamp, he reports that he stopped using the band clamp as the rubber part is tight on the Blue Ox tube.
So it would seem any cap for anything 1 1/2" would serve to keep the inside clean.
I use a tapered rubber plug that I picked up at Lowes. Can't remember what department. Stays better than the original.
Auto parts stores carry a variety of rubber Freeze plugs, which may be an option.
Search google for Rubber Freeze Plugs