According to my callipers, the hex key I have is 0.061" or 1.55mm across the flats, or 0.0675" or 1.71mm at its widest. In a pinch, a T6 Torx might also get in the corners of that hex and turn it, being that it is 0.066"/1.68.mm point to point. We're talking tiny differences here - might work, might not depending on how well made your T6 is.