Adam Hall 5635 Humfrees M6, Rack Insulation Against Ground Loops@+When rack mounting, additional conducting ground connections are created between 19" devices via the metal rails - the most frequent cause of hum noise.@+@+Humfrees interrupts these ground loops. Devices are attached to the rack rails while electrically separated from each other. Additional plus: The front panels of the devices are protected against assembly damage., 4 M6 screws, 4 Insulators, 4 Spacers