Copper Fitting 7/8 to 1/4 (HVAC Dimensions) Reducer / Increaser Copper Coupling & HVAC – 3/4 to 1/8 (Plumbing Inner Dimensions) 99.9% Pure Copper - 5 Pack Compatible with Duct 6" Ideal for Walls & Ceilings:

Ideal for Walls & Ceilings: Designed for seamless installation in standard 16" X 16" duct openings

+ Product Details Size – 12"w X 32"h is the size for the duct opening measurement only

Actual Filter Size – 23 3/4"w x 19 3/4" x 1"

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actual front end outer dimensions are approximately 27

Copper Fitting 7/8 to 1/4 (HVAC Dimensions) Reducer / Increaser Copper Coupling & HVAC – 3/4 to 1/8 (Plumbing Inner Dimensions) 99.9% Pure Copper - 5 Pack Compatible with Duct 6" Ideal for Walls & Ceilings:How to measure HVAC & Refrigeration tubing Refrigeration tubing is measured by it's outside diameter O. D: 1 4, 1 2, 5 8, 3 4, 7 8, 1 1 8, 1 3 8, 1 5 8, etc. Plumbing tubing is measured by it's inside diameter I. D: 1 8, 1 4, , 1 4, 1, 1 1 4, 1 1 2, 1 3 4,etc. Rule of Thumb: "HVAC" nominal tube sizing 1 8; larger than the same nominal size "plumbing" pipe. So for example, a 1 4" HVAC fitting, is the same as a 1 8" Plumbing1fitting. Or a 1 2" HVAC