The GrowSpan Roll-Up Low Pro Tunnel combines functionality with efficiency by providing natural ventilation, security or total darkness just by twisting your wrist.Economical option for protecting delicate plants, extending the growing season or controlling flowering cycles with blackout material. Cover quickly retracts to the peak with our "Twist-of-the-Wrist" feature, providing maximum ventilation, and it can just as easily be deployed. Cover options include 6 oz. black/silver cover for blackout purposes or 6 mil clear greenhouse film. Frames are constructed with 14-gauge, USA-made, triple-galvanized structural steel tubing. 20'W and 26'W tunnels use 1.66" OD pipe. 30'W tunnels use 1.90" OD pipe. 32" clearance on the sides, 5' peak and 4' rafter spacing. End panels are included and feature a zippered section that allows equipment to be easily brought in and out of the tunnel. Heavy-duty ground posts included.