4x4 1.5" (40mm) Rockwool Cube Seed Starter w/ Friction Fit Lid

Printed in PETG with a 0.8mm nozzle and a layer height of 0.5mm (for speed), except the first two layers which use a layer height of 0.4mm (for proper dimensions)

Each wall is two lines with a 0.8 nozzle. Each cell is 40x40mm The floor of the cube holder should also be 1.6mm, but the "floor" of the lid is only two layers (actually the top, assembled). The lid is only one wall thick with a 0.8mm nozzle. 

If you're only using it to sprout seeds and will be checking daily for starts, then you don't really need a transparent lid, but I do recommend it primarily because it makes it easy to see if things are happening without removing the lid, but also if you're a little more casual about checking them they hopefully won't stretch out as much if they get some light.

If everything is printed to spec, the lid should barely fit and the grooves in the thick layer lines will create a nice tight fit. Make sure to clean off any burs or thick strings that might prevent a snug fit. You can technically push the lid all the way down, but you shouldn't. 

I wouldn't recommend direct sunlight - outdoors in indirect sunlight or indoors in a windowsill would be best.