I put my fingers around the outer rim of the reflector and unscrewed it.
I didn't touch the inner part of the smooth reflector.
For me, the smooth reflector is an improvement, the hotspot is tighter without sacrificing spill, and even on low (7 lumens) the lights throws to around 50 or more feet, for 150 hours. On high it just goes and goes. Besides for the "OMG" effect, I can't imagine actually needing more output than the 250 lumens it provides.
Runtime is great too, I used mine for about 30 minutes a day for a little more than a week and it was still going strong. By that time though the low battery warning started to go off every once in a while, so I just popped in a fully charged 18650.
I love my M20.