The 915 S+ is listed at 60 g and the previous generation used in the 913s is listed at 62 g. The obvious difference is the blue to silver color change. The torque range is wider, R flex having a little more torque and the TS having less torque than previously. A little more counterbalancing added to accommodate the increased weight of an adjustable head. In my 915 3H, the R flex feels a little softer than the S+ in my 913 24 degree w/o any noticeable loss of performance.