Why would two allen key sets be different?
I just bought a torque wrench, and I was just doing some bolts up on my bike. I was staring them off with an allen key from a set that I've had for years, and then swapping to the torque wrench to finish them off. There's something weird about them though. When I went to select the bits for the torque wrench, I selected what was supposed to be the same size as the allen key I was using,but it wasn't. It was one size different, even though they were supposed to be the same. Odd.