Hello, I have a 1995 korean Squier 2 procesion bass and I want to make a truss rod adjustment. I have an allen wrench which I though fit but I tried turning it and doesnt always seem to get a firm grip on it. When I took it out the allen wrench had a bit of metal scraps on it. I am thinking that the allen wrench is off by a little bit. I do not want to keep going and end up stripping the head. Does anyone know what size would be needed for this kind of bass guitar?