Quiet!
Very good, quiet fan (as always from Be Quiet).
Quality construction and materials.
Just a little DIY was required: we had to drill 2 small holes and bend the 2 small metal lugs on the Antec Design case to attach it, because while the previous fan, the Antec 3, could make do with 2 screws + 2 lugs, the Be Quiet fan, which is the same size as the Antec, was unable to use these 2 case lugs.
(see photo)