The low-profile compact design of the NEBO Einstein 750 FLEX makes it the perfect companion for any outdoor enthusiast. But don t let its small size fool you ? the Einstein 750 FLEX packs a powerful punch. With five different light modes it s versatile enough to handle any situation. Never run out of light with the flex fuel feature. You can power the light with the included rechargeable battery or you can also power the light with two CR123A alkaline batteries (not included). The USB-C rechargeable battery provides up to 18 hours of use so you never have to worry about running out of power. And with its durable water and impact-resistant construction you can trust that your headlamp will withstand the toughest conditions.