Measurement Guide Example:
When determining vent size, measure the duct opening (width × length) to the nearest inch.
For example, if the duct opening measures approximately 9 ¾” × 3 ¾” or 10 1/4” x 4 1/4, select a 4 × 10 vent.
Vent sizes are based on the nominal duct opening dimensions, not the overall vent face or frame size.
















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