Okay, here is the whole problem with iwaki's ... their naming schemes confuse the hell out of everyone, including me at one point and thats why I held off on a purchase until I knew the exact specs.
MD15R is not enough info. There are R's, RX's and RZ's. R is standard, RX is high flow, and RZ is high pressure. Check the chart:
If you're in the US or canada, you're on the 60hz chart.