The AKG C 451BST microphones are simply a matched pair of C 451B cardiod condenser microphones. A stereo pair features perfectly matched elements with identical frequency response, signal to noise ratio, dynamic range, sensitivity, SPL, etc. Perfectly matched elements provide the best results for stereo miking of instruments, live performances, ambience and sound effects. An AKG H50 stereo mounting bar is included for miking live performances and ambience.