The MAC shear protectors are used to wipe material from the rotor tips into the rotor pockets. This prevents shear between the rotor tip and the airlock inlet. There are two shear protector styles: vented and non-vented.

When it is necessary to vent the airlock's blow-by air, the MAC vented shear protector is used. It vents air from the  empty pocket prior to the pocket refill of product. The vented protector is most frequently used in pressure conveying systems.

When blow-by air is not an issue, the MAC non-vented shear protector is used; most commonly when the airlock is being used as a feeder for vacuum conveying systems or in gravity feed applications.