Just today I got a box measuring 15 x 13 x 5 for shipping three bottles of wine (styrafoam liner). It's three bottles in a row. Uline has something very similar here
http://www.uline.com/ProductDetail.asp?model=S-6715
I travel with them all the time since carry ons don't work anymore, the foam holds the temp extremes from being an issue, and if UPS can handle them cross country, a couple stops at baggage racks isn't going to hurt them.