I got the 305 and I'm happy with it. Here read a reveiw. http://www.dcrainmaker.com/2007/11/r...unner-305.html Here is a link in the reveiw to Amazon http://www.amazon.com/dp/B000CSWCQA?...08ZH443XFE457V& You can get the GSC 10 Speed/Cadence sensor as well. These were safe to purchase when I did it in January. Just check the seller info to be sure because some of these seller seem shady.