I am a mobile mechanic and I use jack stands frequently. I am dissatisfied with the performance of the Central Machinery 3 ton jack stands.
Two sets of jacks collapsed on two different occasions. The first occasion I could have lost my life, within one minute of getting from under the car, the jacks collapsed. The second instance occured as I lowered a car onto the jacks.
These incidents happend within six months of each other and with fairly new jacks. I have looked other places and have not seen complaints about this but I know it has happend to other people and I hope they were not harmed by the faulty design of these jacks.