These are for top loading engraving machines where the engraving cutter knob screws into the spindle from the top. Please choose a tip size when ordering. The tip size will determine how 'wide' of a cut the cutter makes. The taller the letters or characters the larger the tip size should be. For example; for 1/4" tall letters you should use a .020 or .030 tip but for 1/8" tall letters a .010 or .015 tip would be better. All of our top loading tools come with brass cutter knobs.