It’s a 15mm boost driver, potentially intended for 1xAA, 2xAA, and 1xCR123A applications. I have only a limited idea what hosts it fits in though. I was hoping other people would chime in on that, I have very few of those types of light.
Maybe Ultrafire C3 and SK68. Also take a look at comments in my recent 15mm DD+7135 driver thread maybe? [WIP] *15mm* DD+single-7135 driver - single sided Dual-PWM compatible using 3.3x3.3mm FET