Question 1095828
OD Ø = 3.5
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7 x 12 = 84 inches long
449/84 = 5.35 
ID (Internal Diameter): 2 x (5.35/Pi) = 3.4
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3.5 - 3.4 = 0.1; 0.1/2 = 0.05 inches is the wall thickness of the tube.
NOTE: This is a very thin tube, 0.05 is about the thickness of printing paper