913 Weights available are.
4 gram - White, 7 gr - Green, 9 gr - Red, 11 gr - Blue, 14 gr - Black. And there is a 17 gr also available but I believe it's after market. The weight changes the swing weight and will also effect the ball launch height. You can experiment by adding led tape were on top the weight to see how it feels.

it all helps with keeping the swingweight to your liking. i cut my 915D2 down to 44.25" and adding a blue weight to it, feels great!

You know, Sam, when I get notions of changing weights, lies and lofts on my clubs, I go see my fitter and club builder and talk to him. He is a Titleist certified fitter and an old pro at this. I trust him and have known him for many years. He has always steered me in the right direction regarding any changes I am considering. If we change the weights, we go on the trackman to see if the results were positive or not. I believe those kits are still available on eBay.

Todd,
Good idea about the lead tape. I was about to pull the trigger on a weight set myself, thanks