The actual field parts are dia 1.5 steel tube. The team drawings call for 1.25 pipe. Steel tube is measured by outside diameter. Pipe is measured by outside diameter and wall thickness - called Schedule. 1.25 pipe has on OD of 1.66 - 0.160 over 1.50 so it isn’t a match. Schedule 40 (the most common) has a wall thickness of 0.140 for an inside diameter of 1.38 Pipe is cheaper and more readily available (Home Despot) than steel tube. It can also be threaded and fittings are readily available for it.
I wish the tech specs for the pyramid had clearly specified what schedule to use. I have spent some time on the phone this morning with my local steel supplier. He says just go with schedule 40. The outer diameter is 1.66" as specified in the cad drawing, and he says that a 8’ length of it would easily support a 150lb. robot. PLUS - It’s much cheaper! Yea! :] Best of luck to you!