The 2 inch extension is for use with the safety flanges and airway wheel setup. It keeps the airway further away from the buffer and your hands. 
 
Angle Grinder Extender Shaft (5/8″-11)
5/8″-11 threaded
Extends angle grinder shaft by 2″
Allows running two Airway Buffing Wheels at once
 
Attaches to a right angle grinder. The angle grinder extender shaft adds 2″ to the angle grinder's attachment point, allowing a secondary Buffing Wheel to be used simultaneously. Never use a right angle grinder without having an extender to safely push the buffing wheel out and provide a safe distance.
 
Attaching the angle grinder extender to a grinder
Screw the female section down onto the right angle grinding wheel.
Place buffing wheels with center plates, or an inserted Safety Flange, onto the male threaded section.
Secure the buffing wheel(s) with a 5/8″ hex nut or a low-profile inserted flange.