Check out this heavy-duty cage, built by Redneck Mark. He says the bars are 1-inch square tubes:
Redneck Mark is also the man who built my cage. You can read more about my cage by clicking here.
You can reach Redneck Mark at bootsncamo@yahoo.com, or visit his website, www.communityblacksmith.com.
Thats a hot cage! I wish there was a craftsman like that in Melbourne AUstralia!