Kendall Howard M6 Snap-In Cage Nuts - 100 Pack - USA Made
M6 cage nuts can be used in equipment racks that have “Universal Rails.” These are the rails that have square holes punched in them, (rather than the style that has a tapped hole drilled directly in the rail). Cage nuts snap into one of these square holes creating a replaceable, threaded mounting hole for an M6 screw.
Using cage nuts also gives you the ability to choose different thread sizes within the same installation. This is an important point when mounting a variety of equipment from UPS devices to small network switches.