Uses (4) 8x3mm round magnets. I used (2) 8x1.32mm magnets back to back, and used a hot glue to sink them into the far left and far right holes. They were strong enough that I didn't need to put anything in the middle 2 holes. You may need some super glue like I did to keep the magnets in place. I use super glue with 5 second accelerator and it holds like nobody's business. Gorilla (expanding) glue will also work amazingly well but will take longer to dry.
The author remixed this model.
Much larger version to accommodate a lot more poop. Inside dimensions are 97mm x 44mm x 128mm. Also added a 15mm shield at the top to prevent flying constipation offchutes. lol.