Neat, apparently these now come in 6 slot, 8 slot and 12 slot versions.

TB250-BTC is 6 slot
TB250-BTC+ is 8 slot
TB250-BTC Pro is 12 slot

Although, it seems they also call the 6 slot TB250-BTC the Pro in some contexts (the 6 slot ones I have say PRO on the box in giant letters) so be careful