The patches normally marketed under TC's name are .015" and .018".
I use a variety of TC Hawkens and both patch thicknesses work well, however, the tighter fitting .018" prelubed pillow ticking gives me a better seal, a better grip in the grooves, a slight edge in accuracy with a tighter group, so they're what I've settled on for all my TC barrels / calibers, use a short starter with them, etc.