They require 4 inches of 3000# mix. They really can't check the mix but they drill thru and use a L rod to gauge bottom to top. I had mine poured to a spec of 6 inch and 40000# mix. The columns have a large base plate that is bolted to the floor and it has a tie bar across the top with a cable mechanism to balance out the side to side force. The only difference I saw versus the Rotary was the dimensions of the columns that adds vertical or compressive strength. The Rotary's start at 12000 lbs. Back to front set up, lift arms, was virtually the same. I don't think Rotary would risk their rep by selling something dangerous. They both are subject to, and pass, the same US safety regulations and independent testing. I'll test it to the limit before I spend any time under it, including rocking the hell out of my F150, like the shop guys did with their's. Better the F150 than me! Feel free to ask more questions any time.