Review on DOWELL Magnetic Different 180°Measuring Resistant by Jason Spainhour

Got 2 pieces and both pieces don't even fit together when laid flat so don't know which one is right. Most likely, both will make a bad read. Tried it on a clean marble slab and then on a clean glass slab. But both read well when placed sideways, meaning only one side of the piece of metal is touching the surface. It turned out that the yellow plastic part has a bulge, so the metal part does not fully adhere to the surface in the horizontal position.