Cannondale badboy frame size
Hi there, I'm new to this forum and so far think it's a great source of information. I'm going to probably buy a Cannondale badboy for my daily commute to work. I'm just wondering what size bike I'd need. I'm 5'10 with generally normal proportions. (no long arms and short legs here). There's no dealers around here that I know of so web purchase is probably going to be the best bet. I just don't want something too big arriving.
I'm guessing I'll need a large or a medium, but not sure at all. On a standard sized bike I'd probably have no more than 21 inch frame.
Thanks in advance for your help, and sorry if this question has already been asked elswhere.