I've got a new Jamis Renegade Exploit (renegadeexploit). I want to put a slightly longer stem on and I am confused as to what size stem I need to fit my bike. I am not referring to the length of the stem, but the size where it attaches to the bike and the size at the handlebars. Both the fork and handlebars are stock.

The purpose for the switch is to go from a 90 to a 100mm stem. I would like to stick with a Ritchey - either a longer one that is the same as the stock one or an upgraded stem.

Thanks in advance for any advice.