Simply calling the Nitecore EC11 the successor to the EC1 would not even come close to accurately stating the facts. As the first light from Nitecore, the EC11 is not only operated with a type CR123 battery, but also works with a type 18350 IMR rechargeable battery that takes advantage of the special control electronics. Compared to standard type 16340/RCR123 rechargeable batteries of the same size, this high-current rechargeable battery features significantly higher discharge currents at much lower impedance, giving the EC11 a maximum light output of 900 lumens at barely 75 mm of overall length! This incredible ratio of size to light output is achieved by no other flashlight known to us. As an additional special feature, the EC11 also has a smaller red supplemental LED with reflector that can be used as a standby light, constant light, or blinker signal. A type RCR123 (16340) rechargeable battery can also be used. In this case, output is increased by 25% versus battery operation. The remaining features correspond to the high Nitecore standard: Two switches ("On-Off" and "Control"), Cree XM-L2 U2 LED, red supplemental LED in the reflector, 5 brightness levels with type 18350 IMR rechargeable battery: 900/300/160/70/1 lumens, with CR123 battery: 430/230/100/40/1 lumens, removable clip, water-proof to IPX-8, hardcoat-anodized aluminum housing, coated mineral crystal lens. Shipped with wrist strap, spare gasket, belt pouch and CR123 battery. Length: 75 mm, diameter: 25.4 mm, weight: approx. 45 g. Please note that the type 18350 IMR rechargeable battery specified in the descriptions can only be used in the Nitecore EC11. Only the electronics in the Nitecore EC11 are designed to use this unprotected high-current rechargeable battery. Use with other lights creates an EXPLOSION RISK!