Are those investor “class action lawsuits” worth it?

I recently received a letter about a stock I had a few years ago asking to fill out information for a class action lawsuit. Are these things worth filling out? Are these letters a scam? Personally, I didn’t suffer an extreme losses on this holding, but I don’t know exactly what applies here. Basically, it has general information on it the lawsuit and has a form to fill out and send back by a specified date. Anyone have experience with this? Thanks all.