I have 4 of these, and love them.
https://www.fasttech.com/p/1563000 I did, however, break one, by hitting a rather large bump in my truck. Broke the bottom retaining "ring", but I think I can jury rig a fix without having to remove it. Which is probably a good thing, as the 3M tape on this is probably the best I've ever seen, and I live deep in the desert.
Fits most standard mods (nemi, galileo, stingray clone,) without modification. I bored mine out a little wider to fit my K100.