Dialight 550-xx04 Series LED CBI® Circuit Board Indicators. The 550-xx04 series, from Dialight, are 5mm LED circuit board indicators (CBI®). They are in top-viewing, single LED packages. The 550-xx04 family are in a black plastic housing which offers a high contrast. They contain a single colour, 5mm (T-1 3/4) through-hole LED with 2 pins. The range includes general purpose, integral resistor, low current, high efficiency, b-colour and super bright LED options.. Features of the 550-xx04 PCB LED indicators: Top View Single colour 5mm through-hole LED Compatible with 550-xx04-004 quad block