Share 'What size PO Box are you using?'

I'm considering a PO Box for myself as I get more involved with the zine community. Am wondering if it is necessary to get a larger PO Box size or if a smaller size would suffice? Certainly, the sizes 3 IN X 5.5 IN and 5 IN X 5.5 IN are much cheaper to rent but would these be a hassle for zine-type packages? What size PO Box are you using? For you that are using the smaller sized, how has your e…