This is a simple dry erase marker and eraser holder. We kept the eraser and marker on top of the fridge for so long, it just wasn't convenient. We got both the marker and eraser at Target for $1. There is a 22mm diameter marker opening, and 42 x 26mm opening for the eraser. The rear slots are for magnets, I had some from an old iMac display bezel and used those (6mm x 20mm+). UPDATE: I created another version with some of the walls cut out to help save on filament. I kind of think it looks better that way too... ENJOY! I think I will try to make a more minimalistic design in the future, but this solved my issues for now. Hope it can help someone else as well. I have uploaded the .stl as well as .skp file for customization.