A modular synthesizer format which falls into the "small format" category. Originally derived from various standards for 19" rack system based industrial and lab instrumentation known as (DIN 41494 / IEC 297-3 / IEEE 1001.1) and sometimes housed 'Eurocard' technology. Not to be confusedor with the line of low-cost mixers marketed by Behringer under this name. The Eurorack format calls for modules of 128.5mm (slightly over 5") height. Horizontal width is measured in "horizontal pitch", where 1 HP = 5.08mm (exactly 0.2"). 3.5mm mono phone jacks are used for interconnection.