What size stainless allen headed bolts are usually used as the 4 fitted to road bike stems?. I want to replace mine as they are looking a bit dull and worse for wear but I have no idea what size they are?. Had a dig around online and some say they will likely be M5x16 but I have also read of a few other sizes that are possibles?. I once knew a guy who could simply look at any screw, bolt whatever and tell you exactly what size it was but unless a component has the size marked on it, I'm hopeless at that!!. Or is there a way to measure the things and tell?. Cheers.