Compare with normal size air purifier, J900A is much bigger and it adopts durable metal outer case which is stronger than plastic. With such a big size and heavy weight, J900A has 4 pcs omni-directional wheels for convenient moving. 

This item is also featured with 2 sets filters, 1 pc metal pre filter + 1 pc hepa filter+ active carbon and photocatalyst in each side. Everytime the room air goes through from two sides, the dust, hair, pet dander, bacteria that sized bigger than 0.3 microns will be filtrated on the filter. Keep your room air fresh and clean even in colde winter with all windows and doors closed.