All of our gears are "crowned". What you see here is an NOS QP 4th gear next to one of our own QP 4th gears. I used an NOS gear so that there would be zero wear and you can see the dramatic difference in tooth profile and design.
We do the same thing on the straight cut gears. This one happens to be a Cup Car gear but 915 would be the same. We do it for the durability. Relieving the tip like that, in conjunction with the rest of our tooth profile gives a gear that is unmatched in how much surface area it contacting on the thrust face.
Lastly, this will give you an idea of what they look like after REM treatment. As Walt explained it's an isometric treatment that gives it a surface polish to a very very fine resolution. You could say that it's blueprinting something at a microscopic level.
