Streamlight 88049 ProTac 1AAA is a good choice for anyone who needs a compact, back up light without compromising on power. Put this light in your pocket and always be ready to light your way, wherever you go. TEN-TAP Programming Choice with three operating modes: 1) high/strobe/low. 2) high only. 3) low/high. Uses one "AAA' Alkaline battery (include). also accepts one AAA lithium battery. Anti-roll head prevents light from rolling away when you set it down. Solid State power regulation provides maximum light output throughout battery life..