Cathay Pacific Economy clamshells

Cathay Pacific clam shell seats (where the back of a seat stays essentially in the same position, even if the person in it reclines their seat). The advantages of clamshells for leg room for the passenger behind were a big feature in Cathay Pacific's advertising of the new seats - though people with very long legs, like the image author, still have some leg room issues in economy class even with clamshell seats...