B.C.
Honestly, I always just used the black enfamil or similac bag that they give you at the hospital. I started out with the expensive ones, but the black (hides spit up, lol), plastic (easy to wipe) bags made the most sense to me. I only used a diaper bag for the first year and then moved on to a mini-backpack anyway, so things they outgrow so quickly just aren't worth the cost to me.