they are worthless, all of them, don't waste money on those things
Yup. You'll lose more money in running electricity than you'd make with them. Unless you have free electricity, there's no point, and even then, they'll bring in fractions of a penny. They're a nice little thing to play around with when you're new to mining, but unless you're targeting a very new or low profile SHA256 coin, there's not much point.