Chandra ACIS spectra of M33-X7, re-binned for clarity. We have used the four ’gold’ spectra from Liu et al. (2008), corresponding to obs IDs: acisf1730 (black), acisf6382 (orange), acisf6387 (green), and acisf6376 (magenta). The solid lines show the best fitting model to each spectrum, where we have used a standard disc (KERRBB) on the left, and a disc covered by a warm Comptonising medium (THCOMP*KERRBB) on the right. The magenta line corresponds to the mass 15.65  M_⊙ (Orosz et al. 2007, the green line to the mass fixed to 11.4  M_⊙, derived in Ramachandran et al. (2022). We note that every spectrum has been de-absorbed using the best fit model. For each model the spectra were fit simultaneously, with only the mass accretion rate, Ṁ, allowed to vary between them.