Upgrade my Insight M3X to a Surefire X300 Ultra. That light was very tight to put on, so much so, I was worried something was out of spec. A quick call to Surefire assured me that I needed more pressure to get the latch bar to pop up into place, and that the battery cover's gasket will loosen over time. I have a set of Crimson Trace grips coming tomorrow. Anyway, here's how she sits now:

It looks really good. Is that a Smith and Alexander mainspring?

It is.

Wow, good guess, without being able to see inside the mainspring housing. I didn't know they made springs.

He meant the housing, the spring is a Wilson Combat. New Crimson Trace grips.