I like these HAPCO poles that NGrid uses. The poles are universal so they can choose either one or two arms or truss are tapered. For a truss arm, the bottom of the truss just clips around the outside of the pole and the top matches up with the tapered arm. For one arm, the holes on the backside are covered with a plate like above. With two arms, the plate is removed and arm attached with bolts by removed the pole cap. I've even seen poles with one tapered and one truss arm lol.