Like all Woodcraft products, these clip-ons are fantastically well-built and easy to set up. The only negative is that there are only a couple sizes Woodcraft make that do not use spacers, and there is no way of knowing which come with spacers and which do not. So in my case, I bought 30mm clip-ons, and they were actually 34mm bases with 2mm spacers included to bring them down to 30mm. Even with spacers they fit really well, I was just hoping to have exact-fit. Fantastic for vintage race bikes.