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 Universal Inline Bracket adapts TETRAD cartridges for many BSR tonearms that use a single screw visible from the top that secures this bracket through the center of the headshell or shroud.
NOTE: this is generally found in older style phonographs/record players that use ceramic cartridges, not usually modern turntables that use magnetic cartridges.