1/4 in (6.4 mm) bearings allow bearing holes to be made in round duct with the use of a scratch awl. Squeeze pipe so that it is oval shaped. Insert damper into pre-punched bearing holes. Pipe will spring back to round when released. Secure with wing nuts provided. Damper may be adjusted with screwdriver or optional damper handle. Available with or without handles. Dampers are designed for forced air systems, they are not capable of being used in wood, coal or other similar systems.
Single bearing|Caution Malco dampers are designed for forced air systems, they are not capable of being used in wood, coal or other similar systems
Malco Standard Warm Air Damper, 6 in Damper, 28 ga, Domestic