api 500 slotThe 500 Series, also known as the lunchbox format, refers to a standardized, modular audio equipment format used in professional audio recording and processing. It was orinallyFrom the inventors of the 500-series format, the API 500-8B lunchbox is an 8-slot, 500-series energy rack desned to just accept all API normal 5.25″ X 1.5″ modules, permitting you to confure a recording or mixing package to fit your