i was not able to find any reviews on these so thought id do one.
Sold as "Air Filter Box Intake Cleaner For GY6"
The rubber hose going to the carburetor has a diameter of 44mm giving it an area of 1520.5mm for air flow.
The rectangle on the other end is 40x65mm giving it an area of 2600mm for air flow.
The box looks and feels to be of acceptable quality for the price.
One thing it was missing is a gasket for the lid and it definitely needs one.

 

use rim grease instead of a gasket since you will probably never find anything that works.. Yo can get it at any motorsports dealer and its designed for sealing airboxes