SH SC 1 is a twin disc cello transducer with 1/4“ socket. The sensors (20mm) mount easily on the soundboard of the cello. Easy installation. Includes an attached 1/4” (6.3mm) output socket. Soundboard transducer for cello diameter of transducers: 20 mm length of cables: 24,5 cm output connection: 6,3 mm (standard)