'B' stock merchandise is stock that the manufacturer can't sell as "new". There are undoubtedly many reasons why something would be classified this way, but some of the most common are returns based on money-back guarantee policies or defects in the original operation of the unit, or aesthetic damage during shipping etc. For the most part, the worst that will happen when the unit shows up is that it will have a scratch on it, though in my experience of buying 'b' stock items, I've never even exeperienced that. You tend to get a shorter warranty, and there is some risk, but it often represents a chance to save a significant amount of money on something that is indistinguishable from new.