Although I believe that these mod kits are a very cool idea, I think the execution could be better. I mean, these kits are made to take the work out of modding, and despite the pro of having only a screwdriver as a necessary tool, they take the creativity factor out. In addition, I think that they could have chose more traditional materials (ABS or PVC) as with custom milled aluminum is just way too expensive. $17 for something you can easily replicate the same ranges for by just going out and buying a suitable replacement spring for 3-4 dollars is not worth it in my opinion. That said, I think that did a great job on advertising and allowing for nerf youtubers to test.
For what it's worth, it's not just extra range we're aiming for, but increased durability as well. But hey, to each his own.