Once piece elbows are fabricated from a single piece of galvanized sheet metal. They are formed into an elbow by a special machine. Centerline radius is 2.5 times the elbow diameter. All elbows 4” dia. to 8” dia. are 22 gauge and 10” dia. & 12” dia. are 20 gauge. Each elbow is welded air tight on the back. Long radius elbows are male ends but can be purchased with male and female ends if requested.