I made a vid on my process(of course) where i dyed the top layer of 5. I added a 6th ball to finish up the partial skein i had left. It used up quite a bit of yarn, i haven't put them to use yet but soon...lol.
These are said to replace fabric softener, decrease drying time and help increase fluffiness while reducing static among other things. You would throw them in the dryer and while bouncing around with your clothes that would help the hot air circulate cutting down on drying time. As with most things, the more the merrier(and the bigger the better i assume lol).