Hey guys, a little off topic but few things I have noticed and heard regarding the X vs M proline compound. You always want to choose a hardness based upon temp (i.e. 4,3,2). Then you want to choose M vs X based upon moisture in the track. M is primarily used for wet surfaces and X is for dry. Also X is slightly harder than M at the given compound. I have also heard X doesn't expand as much as M which might provide more stability at high RPM .