This is a replacement lid closer for the 30oz Milwaukee Packout tumbler. It might work better on a smooth print bed but I only have a textured one and it seems to work OK. The hole in the handle part is to insert an 8mm x 2mm neodymium magnet and the round plug is to insert after the magnet. Before pushing the magnet down in, make sure it is oriented to be attracted to the 2 magnets in the lid itself. Before inserting the plug the whole way make sure it is turned so that the downward sloped part is pointed towards the outside of the lid as it is very difficult to remove or rotate after it is pushed the whole way down.