Read more 4″ x .024 Aluminum Corrugated Round Elbows, Select Colors The average installation requires two elbows at the top and one at the bottom. If you are connecting your downspout into a drain tile, the elbow at the bottom is not necessary. The offset is the measurement of two connected elbows; 40 degree elbows have a 3″–9″ offset and 72 degree elbows have a 9″ offset. The degree of elbow you use is determined by the overhang of your structure. To determine the overhang, measure the distance between the wall of your building and the back of the outlet. An overhang of 9″ will require 2- 72 degree elbows. If your overhang is greater than 9″ you’ll need to insert a piece of downspout between the elbows. An overhang of less than 9″ will require (2) 40 degree elbows. This elbow combination also works when making a transition around a ledge or other protrusions. You’ll need to reduce the size of the opening on the elbows and downspout when using either corrugated or smooth options. (see Product Description below left and our Elbow & Downspout Crimper Tool.) Note: These Select Color corrugated aluminum elbows, shown here in Grecian Green, are priced the same as our Standard Colors (see Aluminum Color Chart below), but due to the machine setup required to produce them, there is a $100.00 up charge (one up charge per color, per order, covers elbows and downspout in the same color). To order Corrugated Select Color Elbows, please call us at 269.665.2700.