They are just the perfect size for my yarn and needles for sock knitting, but I have also made them for family members who use them as washbags, makeup bags etc.
They measure about 9" long x 4.5" x4.5". I like to add a co-ordinating zip (it is a great way to use up odd zips that I don't know what else to do with!) and a zipper pull made with beads.
I absolutely love these - I have another (cough, cough) six cut out and ready to sew, and more than twenty (what?? How many??) matched up pairs of fat quarters and zips. It's an addiction I tell you. I can't help myself :)