I shouldn't say this, but I've never broken a chain on a ride in 45 years of owning a "10 speed". I don't find it necessary to carry a tool. That said, I have a Park CT-5 that resides in my tool box at home. I've used it often enough and never had a problem with it. I had an older generic chain tool that broke the first time I tried to use it on a modern 9 speed chain to remove the extra links on a new chain. Those pins are much tougher than the old 5 speed ones.