Not sure if this is in the right place, but I was thinking about buying the egg foam to ship eggs in and they state it fits perfectly in the #7 priority mail box. I have looked on the internet and can't figure it out and the P.O. is closed today. So, I am turning to my BYC friends for help! Is this the medium flat rate box? I'm just trying to figure out if it is worth it or not, because although I could ship more eggs at a time, I would have to charge more for shipping. Any advice is greatly appreciated.