Dialight 555-2 Series LED CBI® Circuit Board Indicators. The 555-2xxx series, from Dialight, are PCB LED indicators from their CBI® circuit board indicator family. They contain one 2mm (T-3/4) LED in a black plastic housing. The housing positions the LED at a right angle to the PCB. The 555-2xxx is available in general purpose and integral resistor LED options.. Features of the 555-2xxx PCB LED indicators: Through-hole mounting 1 x 2mm (T-3/4) LED Black plastic housing Right angle Variety of colours High contrast between LED and housing Compatible with 555-4xxx Quad Block