Cho was researching Muggle prosthetics and Hermione helped her look through the books and pamphlets on the subject – Cho's injury wasn't old enough or healed enough for her to be fitted with a prosthetic, and it would be very difficult to arrange during the war anyway, but one day they could do it. Cho was amazed by the advanced nature of Muggle technology and Hermione, for her part, paid particular attention to the hand prosthetics. They weren't half as good as the ones for leg amputations – hands were so much more complex than legs and feet and there was only so much Muggle technology could do. But they were better than having no hand in Hermione's opinion, and the technology was always improving.