Jiffy Regulator 1/4" - 8039 Duro Dyne 1/4" Jiffy Regulators are ideal for controlling small dampers up to 10". They are suitable for both round and square ducts. Sold in packs of tenFeatures: -Solid threaded end bearing. -Rugged forged wing nut. -Inner and outer washers for strong support. -Formed steel handle keys into outer washer.