The reel is made of 1-1/2" (approx 1-3/4" OD) steel EMT (ElectroMechanicalTubing) with a 1/4" slit nibbled lengthwise to capture one end of the tarp. The gray parts are 3D Printed ABS and the "hubs" are pressed into the ends of the EMT. In use the tarp is unrolled back over the trailer...