We use a virutex one. It is a squeezy sprung job and works very well for us. Certainly a step up from the bearing guided router bits I used to use. I also have a different single bladed device that I think came from Rutlands some years ago. Chrome handle and white plastic triangle, under a good quality blade. Works well too but not as quick as the virutex one. There are a lot of choices, and a lot of them are similar to the virutex but I have no experience of them so couldn't say...
I think i paid £15 for mine.
HTH
Neil