I've had a Fenix LD01 (1X AAA flashlight) for some time now, and all I can say, it's excellent! For an EDC, it is essential (to me) that it is as slim as possible. No CR123A-lights as an EDC for me, too chunky.
The LD01 has excellent threads too, and the beam is excellent!
It has "just" three modes, medium on start-up, second is low, third is high.
It works excellent on 1X AAA, either alkaline or Lithium primary (1.5V!!)
Do not use rechargeable Li-ion!
Use a NiMH 1.2V battery instead, this is the way I use it. It works flawlessly.
This light is that slim, is will fit any pocket. Length is less an issue than diameter of the light, is what I have noticed. I've tried many, many lights as EDC, the only
true EDC (read: ALWAYS on me) I have, is this LD01...
Other lights travel on a regular basis in my jackets, (ranging from E1E to C3 Centurion or WE Sniper MC-E) but... the LD01 is really always in my pants-pocket