Would be nice to include in the kits
Crutchfield Customer Review (What's this?)
It's a nice to have but not a necessity. It's great for flat panels, but those are few and far between. Once compound curves or tight radii enter the picture away goes the roller and out comes the hand. It's more of an addition to, than a need to have.
Pros: Helps with firm pressure especially on flat panels
Cons: For what it is, it's not necessary. It helps, but some firm pressure with your hand does just as well