.
IMPORTANT REVISION:
Added to my original review post:
^ Filter manufacturer's cutaway illustration to show correct orientation of filter ^
Forge UK, contrary to Forge USA, initially advised the opposite orientation! To be fair, it is very ambiguous and, to date (early September 2010), tests have shown that reversed orientation is not detrimental to function nor performance in any way. Obviously the filtering ability remains unchanged and any changes to flow will be minimal, likely imperceptible. This is now Forge's official position.
I am expecting to hear from Forge soon about their position and advice regarding those of us, includes me, who have their filters the 'wrong' way around.