I did not managed to open up the box to have a look but from the outset, the air filter seems appears to consist of 2 separate pieces of rectangular shaped paper type....I believe the regular has an 'L' Shaped. I have not sourced for the BMC option yet.
However the CF box although huge is in fact really light. The internal reserved storage volume of filtered air before the throttle body intake is really 'volumous' too.
This could perhaps explain the highly responsive initial power surge whenever one takes a quick but short stab (without flooring) at the throttle even at 2nd gear from a standstill.