Common mode choke is an inductor has two windings. Two windings in the same direction when in or out. Load current produces load magnetic field which will cancel each other, so the choke will not affect the load current. While common mode current will produce magnetic field will strong each other, that is a larger impandence will occur in the core, the common mode current then being blocked.
Common mode choke made of king magnetics nanocrystalline core have much higher inductance than traditional cores like ferrite core, so more common mode noise will be filted. Nanocrystalline core is also a green product, energy saving and low carbon emmision.