Feature:
1) Aluminum alloy material.
2) all the mutil-vane dropping naturally ,aviod the interior and exterior air to exchange
3) Design for uni-directional and non-return air flow ,
4) Can adjust the atmospheric pressure automatically, between the indoor and the ourdoor.
5) square or round shape upon available
6) Natural anodized aluminum finish or powder coated

Construction:
Outer standard Size: As per your request(Face size=Neck size+60mm)
Neck size: A*B(size is as per your request)
Net space of vane arbor: 49mm
High:50mm
Edge width: 32mm
Order Notes: Item-neck size A?B-color/(OBD/filter or not)