I agree with all the reviewers here. I am also a tool junkie and have other styles and brands. I didn't have the plunger style of plier so I purchased one of both sizes offered here.
I have used the larger size about 20 times or so for palmering hackle. The stem has never came out of the grip of the plier unlike the other ones I have.
I don't know if its just how my hands are built or what but my hackling has been way better using this plier. I seem to have better stem control if that's a thing. Its easier to straighten out a twisting stem. Maybe its the rounded shape.
Bottom line is my tying has improved a bit using this tool. It seems pretty solid to me. Stonfo in my opinion puts out some pretty good tools. I don't think anybody will be disappointed with this addition to their tool arsenal.