Well, they're now sold, but to answer your question... These basically move the cantilever bosses up so that your brakes would be in the right place to work with 700c rims. As for tyres, I doubt you'd get the modern chunky 700c gravel tyres in there, but that's more to do with the retro 26" frames/forks which were never designed with that in mind. I would think you could probably get CX type tyres in there, 700x30-32c perhaps.Excuse my ignorance here so with this booster I can put 700cc wheels on any 26inch frame and forks with any brake calipers I want also can you get thick tyres like mountain bike ones for 700 or do they just take thin ones cheers