TC9 uses a slightly shorter T-yoke than the 3HP and 4HP, they are disigned for two 1" slugs for a total of 200oz of ceramic ferrite. while the others use 3 3/4" mags.
TC9's have a xmax of 29mm's. That’s when 50% of the coil has left the gap, or 70% Bl or 3% THD. A fairly common standard among honest manufactures.