ArtboardRange Question

I'm having an issue with saving out SVGs, I've stripped it down to the code below.. My end goal is to loop through multiple artboards in a master document and save out SVG files for each. Looking at the scripting reference it says under the export options that artboardRange accepts a string of comma delimited artboard names. So just trying this:

var doc = app.documents[0];
var fileSpec = new File("test");
var exportOptions = new ExportOptionsSVG(); 
exportOptions.saveMultipleArtboards = true;
exportOptions.artboardRange = "300x250,160x600";
doc.exportFile(fileSpec, ExportType.SVG, exportOptions);

with artboards named 300x250 and 160x600 (or even just one, "300x250") gives me an Illegal Argument error on line 6. I'm guessing it's the artboardRange line causing the error, what would be the correct syntax there?

thanks!