One thing important to remember about jack stands is that high quality and older American made jack stands were rated as EACH. In other words a jack stand that said it had a 3 ton rating would actually hold up 3 tons.
Now, most of the new jack stands, and especially any foreign made jack stands, are rated as PAIRS. This means that when they say 3 ton capacity that means that each jack stand will only support 1 1/2 tons. Be sure that you check to see how your jack stands are rated and it is always a good idea to use stands that are rated at TWICE the capacity that you think your vehicle weighs.