FrankH's links are helpful. I had this on my trek 7000. It is the 23mm parallel disc mount. Hope down to the LBS and they should have one cheaper than 25. I got mine for something like 15. Ebay too has some, just look around. As far as universal bolt-on disc brake mounts, i do not feel that they are needed and cost a bit more too. Mine works just as good as on my other system that is the standard mount. No worries there.