HFC refrigerants such as R-404A have come under scrutiny due to high global warming potential and relatively high leak rates in supermarket systems. In Europe, several design modifications such as cascade systems and new refrigerant choices are being investigated. One of the leading options is to employ a cascade or hybrid system using carbon dioxide (CO2) on the low temperature refrigeration side and R-134a in medium temperature. R-134a has higher efficiency than R-404A and about one third the GWP. To make even greater gains in GWP reduction, a new lower GWP refrigerant XP10 has been developed that has the potential to be retrofitted into the medium temp R-134a circuit with minimal to no system changes. This refrigerant has less than half the GWP of R-134a, has no ozone depletion potential (ODP), and is also non-flammable. It can therefore be used in existing supermarket systems with large charge sizes without concern for flammability. Toxicity has also been fully characterized and it is anticipated it will be an ASHRAE class A1 refrigerant. This report will show results of experimental performance testing compared to an R-134a baseline in a supermarket system.