Stock units are fine...if your hair specs fit the color and density. And if your bald area is no larger than the stock area, usually 8"x10". They can be cut to fit. The hairline can be an issue, whether you need an A or CC contour. They cut and wear the same as customs. BUT, if you need a non-stock density, color(s), gray, temple flaps, etc., and don't want to cut to fit, custom is the way to go. But it takes longer, and has more margin of error.