R508B

General Information.
R508B is an HFC/PFC (Perfluorocarbon) blend designed to be a replacement for R503 or R13 in very-low-temperature refrigeration systems, typically the low stage of a multi-stage system. R508B has properties similar to R503 and can be used to replace either R13 or R503 in an existing system. POE lubricants should be used, and it may still be necessary to charge hydrocarbon oil additives to ensure proper oil return. 

Features and Benefits.
- Substitute for R13 and R503 at very low temperatures (-400°C to -1010°C)
- Azeotropic blend
- PFC-based refrigerant
- Offers advantage over R23 including significantly lower discharge temperatures
- Non-flammable, non-ozone depleting, safety classification of A1
- Compressor to be charged with POE oil