3 1/4” overall. Black anodized aircraft grade aluminum construction. C4 LED with up to 160 lumen output. Fast, safe, adjustable, secure side mounting to 1913 and Glock style rails. Fits existing light bearing holsters. Momentary/steady on-off switch. Up to 2 1/2 hour run time per battery set. Uses two CR123A batteries. Lithium Metal with package.