The only downside to Jewel is the fact that
it is quite difficult to install and adjust.
Same thing with the Geiselle or any adjustable trigger, how well it works comes down to how good you are at the install.
The Timney one piece is the best no brainer trigger that I have ever used, nothing to adjust and super easy to install and works perfect for any AR application.
I agree completely. Adjustable triggers can be difficult to work with. I have a Timney Gold in my SPR. No creep, no stacking just a consistent trigger. I love it.
Note: I am surprised no one has mentioned the Chip McCormick trigger. It is non-adjustable as well. I don't think it is quite as good as the Timney Gold but it is growing on me now that I am used to it in my DPMS .308. It, too, is quite consistent. Both are easy to install. It is another option to consider.

