The exterior dimensions of the Audio-Technica AT8109 Foam Windscreen are 0.39 x 1.0" (10 x 25mm) and the interior dimensions are 0.33 x 0.74" (8 x 19mm). It fits on Audio-Technica microphones with the M25 and M26 case style, such as the ES933 and ES943 gooseneck mics.