The one that is most appropriate will largely depend on your breast size, but remember to give a little extra room for breast growth, which is common during the breastfeeding stage. (mombible.com)
And get this: you can also lay these small breast milk storage bags flat for extra room in the freezer! (geekwrapped.com)
It's a good idea to give a little extra room in the rise and hips with fleece so that your child has enough room to move around because fleece is not stretchy. (the-cloth-diaper-connection.com)