Idk, these have a wider base than the 6 ton jack stands. I have an 88 camaro up on them now and I really have to push on the car to get it to move in the slightest. And the jacks aren't just sitting on top of the blocks, I cut the wood real tight so I have to hammer them into fit and hammer them back out. I'm scared to death of slowly suffocating under a car but these seem totally safe to me.