Tier 1- slide lightning, ball nose front and back, 90degree the top, striker and lower spring, trigger group, spring kit and bar, warren sights, Tin pin set
Tier 2- less lightening, tier 2 trigger, grip modes,
Tier 3- polished and tuned, 5.5 lbs tigger, grip modes
Just some of the differences they offer between the packages. They have spent a lot of time and resources to fine tune a great product. They don't just make cuts in the slide to look cool but to have a functional purpose to them. The parts aren't just randomly put on but tested and evaluated to get a good end result. There is nothing wrong with a stock Glock, they just made more improvements to it. Feel free to call them and they will go in-depth with you about the various tiers and why they did what they did. These tiers aren't for everyone but some will like it. IMO they have spent a lot of time on R&D with their products from the Glocks, M2's to the LVOA rifles.