Timney, Rifle Basix, and/or "tuning" the OEM trigger with kits etc. Those are the three most commonly used. I prefer the Rifle Basix SAV-I but since I have not used a Timney can't say whether it is better or not. FWIW I just traded for a new Axis and the trigger is much improved over the ones I got a couple of years ago. It is good enough for me not to invest in another trigger.