From the Manufacturer

Used in every dust collection system to control air flow from one machine to another, blast gates maximize system efficiency. We offer blast gates in both black ABS plastic and aluminum. Plastic blast gates are economically priced, have a textured surface and an easy sliding gate action. For those customers who prefer metal, our top quality aluminum blast gates feature a cast aluminum body with steel gate and locking knob. Our blast gates are fast movers!
4-Inch outside diameter
Easy sliding-gate action
Economically priced
4-Inch OD ABS plastic