7/8 Inch (HVAC Outer Dimension) 3/4 Inch (Plumbing Inner Dimension) - Copper Long Radius 90° Elbow Fitting with 2 Solder Cups For Plumbing & HVAC – 99.9% Pure Copper - 10 Pack Floor Register / Modern Victorian + Product Details Size –

+ Product Details Size – 24" x 24" with 12" collar T-Bar drop ceiling perforated return grill - metal back casing

+ Product Details Perfect Fit & Easy Sizing - Designed for a 28" x 10" OR 10" x 28" duct opening (measured at the opening)

actual front end outer dimensions are approximately 12 5/8" width X 32 5/8" height -

Item Size: 155 x 69 x 60 mm

7/8 Inch (HVAC Outer Dimension) 3/4 Inch (Plumbing Inner Dimension) - Copper Long Radius 90° Elbow Fitting with 2 Solder Cups For Plumbing & HVAC – 99.9% Pure Copper - 10 Pack Floor Register / Modern Victorian + Product Details Size –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