I used 1,5 ID schedule 40 PVC so the OD is around 2inch. one thing I found is to be sure to use a pretty heavy piece of strap metal to hold the pipe down. I used 2" single wall black pipe cut 1.5 inches long and welded this to a piece of strap metal 2*3_16 3.5 inches long with a 1_2 inche hole in one end for bolting on to sickle mounting brackets
