Duro Dyne - 1/4" dial regulator sets and bearings (for dampers up to 10"):These heavy gauge plated steel regulators are among the most popular on the market. They minimize air leakage and reduce rattle. A wing nut locks the damper in position, yet permits quick readjustment. The dial shows the damper position at a glance. The regulator mounts easily on round or square ducts.
Warning: this product contains a chemical known to the State of California to cause cancer. P65Warnings.ca.gov