I for one, am VERY glad to see Dan make the spine on the reg series rounded and not flat. The rounded spine does NOT leave a groove in your thumb if you are pressing to hard. And it is easier on your baton and it will last longer if you are whacking the blade throught something. This may not sound like any big deal, but it COULD be if youy were in an area where suitable baton wood was hard to come by. Over all, I just think the rounded spine is more user friendly. Thanks again Dan for a well thought out design.