"If you've got a set of Harbor Freight jack stands somewhere in your garage, stop using them immediately because many of them have just been recalled over pawls that could "disengage from the extension lifting post" under a shift in weight, causing them to suddenly collapse. We feel like this shouldn't have to be said but we'll say it anyway: bad jack stands that could suddenly fall are extremely dangerous and being underneath a car supported by one could very easily result in serious injury or death.
According to Harbor Freight, the recall applies to three-ton and six-ton heavy-duty steel jack stands with item numbers 56371, 61196, and 61197. The number on the three-ton units can be found on the label at the top while the six-ton stands have their numbers printed in the yellow section of the label found on the base."

I have had mine for a few years, and used them many times without incident, but back they go. No receipt needed. My 3 tons are the 61196 models. I just finished a complete brake job on them with a GMC just the other day.
Harbor Freight Recalls Jack Stands That Could Suddenly Collapse - The Drive