This product allows for proper mounting of your Tetrad cartridge. It is one of 3 different styles available to allow attachment to most any tonearm. It goes between the mounting at the end of the tonearm and the top of the cartridge. This is for 1/2" mount.NOTE: this is generally found in older style phonographs/record players that use ceramic cartridges, not usually modern turntables that use magnetic cartridges.