4mm/ft scale or OO/EM/P4 gauge Colour light signal head with two apertures, either representing a two aspect version (with a red and green light) or a 4 aspect signal (with the bottom hole featuing a red and yellow light and the top featuring a green and yellow light) - allowing the signalling sequence of Danger (red) - Caution (single yellow) - Warning (double yellow) - Green. Drawn using official technical drawings from Unipart Dorman - who supply these to Network Rail.
If you choose to put LEDs in the signal to make it work, I recomend these
or simliar. There is enough room in each chamber for two of these LEDs, allowing you to make a 4 aspect version.
Note, this model come unpainted and without and LEDs.