I built a singlespeed bike a few years back, mainly from surplus parts, but I had to buy some brake callipers because I didn't have any spare at the time. I wanted to spend as little as possible so I bought a pair of cheap Campanolo Veloce ones. They did the job but they felt a bit flexy/'spongey' compared to the better quality callipers that I am used to. They are also black, and I prefer silver. Since then I have dedicated an old bike to turbo trainer duties so its brakes were no longer needed. I decided to pinch the callipers off that bike to use on the singlespeed instead. I swapped them over today and they feel a big improvement. It turns out that the old brake blocks were pretty worn, so they would have needed replacing soon anyway. If I ever decide to take the old bike off the TT I can put the Veloce callipers on that.