I was pretty disappointed to see that the bolts/washers that attach the RAI to the wing only lasted a couple of weeks of a Scottish summer before starting to rust.
The Mantec badged one comes with caps that plug the holes preventing water ingress.
I emailed them to ask if they had any for the LR one also as I think they make that one too – it’s on their website…
Anyway they didn’t reply so I bought a couple of these end caps which fit perfectly (just sliced a couple of mm off the end internally to match the hole depth).
The hole diameter is 20mm and plug size refers to the end cap outside diameter which is 22mm.
Of course stainless fixings is the way to go but these keep the water out and the bolt heads away from prying eyes…