Two versions of this object are available: v1.0, which is NOT stackable and doesn't have a window v1.5, which is stackable and has a viewing window

These are designed to fit a 4x8 bubble mailer laying down and are able to be printed on a stock Ender 3 bed. You may need to increase the bed size in Cura/your slicer to 225x225 in order for it to fit but it will.