Most mobile CB aerials have a 3/8" thread on the bottom - matching the 3/8 dome and RM dome mounts. The RM dome (Rear Mount Dome) allows you to vary the angle of the aerial and tightens with a wing nut. This means you can mount it on sloping panels and still get the aerial standing up straight. (An alternative way of angling an aerial like this can be to use a standard 3/8" dome, with our angle adaptor).

It is made up of a DV dome with a 3/8" adaptor and the wing nut & bolt.

The PL Dome is for use with PL connecting aerials, like the Sirio Hi-Power.

All of the dome mounts are the same in the way they fit to the vehicle, a three-pronged "washer" is designed to tighten up on the underside of the panel and make the earth connection. This is where you will need to get a good metal-to-metal connection between the prongs and the panel and protect it against oxidisation if necessary. (Update Feb 2013 : We've noticed new stock of Sirio dome mounts now have a single big nut with serrations on one side, which takes the place of the 3 pronged washer, lock washer and nut. For the moment, some have the new singe nut, some have the old 3-piece arrangement. When all stocks have the new tightening method, we'll update this info.)

The best way to do this is to paint over the whole area where mount and panel meet with a zinc based paint (Red Lead, or many other rust inhibiting paints will do.) Alternatively, use a spray-on plastic seal spray.

A small right-angled plug connects to the mount, so you need less than 35mm clearance between roof and headlining to fit it.