These magnets are intended and tested for use with magnetic trays and GW bases as a point of reference. Of course, you can also use them to magnetize turrets, weapons options, and other modeling shenanigans.
These 3/16" x 1/16" N52 are a little smaller, leaving about 1/2 of a gap in height on most bases. When there is a gap, it is highly recommended to use Green Stuff to help hold the magnet in place, as thin super glue (cyanoacrylate) tends to be brittle and the magnets may snap off.