It can be used for a couple of things. First would be to change the swingweight of the club. Some people like a heavier swingweight and a heavier weight will make this happen. More commonly, the weight is changed along with the shaft to keep the swingweight the same (about D2) as standard. If you put a heavier shaft in, you need a heavier weight to keep the swingweight the same. A lighter shaft requires a lighter weight to do the same.

Curious question for the techies - will using a 14 g instead of a 12 g draw/fade weight increase the draw/fade, or would any weight provide about the same balance and just change the SW?

Hi Don, Great question. The weights use the same balance of weight on each side so the result is that only the swingweight is changed when using a heavier or lighter weight.

What is the standard weight for the 917D3 driver 12g?