Can anyone tell me the best fit for everyday metal type frame for glasses?

These are the best fitting I have found for metal frames

Do they fit Oakley Radar sunglasses that have rubber on the end?

Yes they fit almost everything. I have oakley flatjackets and m2 frames and is perfect. All you have to do is put hand sanitizer inside the holes so it can easily slip in.

If they adjustable, what size is average to ordet?

I found that it really depends on what you want them to do. First, I have an average size head at about 22.5" in circumference. Average male range is somewhere about 21" to 24". I then decided I wanted a cablz that I could use that would hold my sunglasses snug but also have the ability to hang down around my neck for this I choose 12". They hold pretty snug so they don't move around a lot when boating, golfing etc. The other cablz I choose was an 18" these I use when I want the ability to take them off with a hat on but can still tighten so if they do come off you don't lose them. I suggest you go to their web site it does have a fitting guide because another factor is the size of your frame ends. Good luck