I know The Mouse Factory vaccuum seals each tray. I would think they must slightly pre-freeze Bryan as if not the rats on each styrofoam tray would stick together and freeze in a lump. Since you can open the package and sort of pop one free then they must be partly frozen first, then laid on the tray and vac packed then.

Here's a link showing their packaging.

http://www.ball-pythons.net/forums/s...=mouse+factory