Sonostar developed the Megahubs for those who are specifically looking for a hub that can accommodate either a 1" or a 1 1/2" PVC pipe. They are engineered to support much heavier loads than the 1/2" hubs. The megahubs are made of strong and durable white ABS plastic. They have holes for nuts and bolts built into the design, and the top hole is tapered, so that the bolt head will be flush with the top of the hub (so it won't rip or tear the cover). There is also an arrow on both the top and bottom of the hubs to help you position your drill bit when you go to make holes in your pipes. The Megahubs come in 4-arm, 5-arm, and 6-arm configurations. There is a 12 degree angle built in to each arm, which helps bring curvature to the dome or sphere as you build it.