Though the naming conventions may seem confusing at first glance, the following key should make your C-star configuration and purchasing process much easier!
The letters following the serial number designate the depth rating of the transmissometer and the wavelength of the LED.
P: Plastic housing rated to 600 meters
D: Deep (Aluminium) housing rated to 6000 meters
R: Red LED, wavelength 657nm
G: Green LED, wavelength 532nm
B: Blue LED, wavelength 470nm
Serial number examples:
CST-1236PR – Plastic unit, 600 meter rated, red 657nm
CST-1219DG – Deep unit, 6000 meter rated, green 532nm