Mike,
I think this is the one I have:
http://www.sparcousa.com/product/r-323
I just walked down and measured it, and it's 13.5" outside diameter. Depending on how they measure, that's probably about right since the 330mm translated to about 13".
I'm sure I will break something else before it's all said and done. Hopefully not soon though. I need to arrange an alignment this week, then I'll start driving her pretty regularly!