This product is very much a run of the mill effort from somewhere in China.
Each stand is rated to a capacity of two tonnes (four tonnes per set of two). They are manufactured to a British Standard: BS AU223a 1995. Draper says you should not use more that one set on the same vehicle so you will not be able to get a vehicle off all four wheels with these stands. Minimum and maximum heights are 278mm and 405mm respectively.
Some people will worry about the easy ratchet style mechanism but the pure physics of the product means they will work just fine.
Quality of manufacture is indifferent: The moving "ratchet bar" supports are cast metal, roughly molded, and are poorly painted. The base body is made from folded sheet metal welded on the joints. The welds are uneven and poorly done.
There is a tab formed in the sheet metal of the base at the neck of the stand and instructions on an attached label to bend this tab over to trap the moving ratchet bar once it is inserted. I found this "self assembly" requirement disappointing. The tab can be levered with a large screwdriver. The only reason for this is to allow for smaller packaging. You could leave it alone since it makes them easier to store and makes no difference to their opperation.
I gave these stands three stars because a little more care in their manufacture would make them look like they were put together by someone who cared about their work. I haven't sent them back because they are, after all, a generic product intended for rough use and the price wasn't bad.