The Nitecore E4K is newest flashlight from the E (Explorer) Series and it has been quite awhile since the E Series has been updated with a new model. The threads and o-rings were well lubricated. Threads were rather smooth and clean (no gritty feeling at all).

The integrated advance temperature regulation (ATR) technology regulates the output of the E4K according to the working condition and ambient environment to maintain optimal performance. Nitecore did not disclose the tint (color temperature) and/or the CRI (Color Rendering Index) for the LEDs used in their light. For this light, a guesstimate would be in the 6500K and 70CRI ballpark. Batteries Required: 1 x 21700 15 A lithium-ion (included) or 2 x CR123A lithium metal / 2 x 16340 lithium-ion (not included)Five brightness levels and three special modes are available, which are controlled using the updated two stage side switch. To turn the torch on fully press the switch and it will come on in the last used brightness level. Once turned on the brightness level can be changed with half press of the button to cycle through ultra-low, low, mid, high and turbo. Instant momentary turbo access can also be achieved by half pressing and holding the button with the light on, or fully pressing and holding the button with the light off, and once released the light will go out. The new design of the popular headlamp provides dual primary lights; a spotlight and floodlight. The dual primary lights can be used together or independently, achieving the ideal combination of long distance throw and flood beam. In addition, the NU25 hasa red light for map viewing, emergency use, stargazing, wildlife observation and night photography. HOLD – Mode change (light cycles through ULTRA-LOW, LOW, MID, HIGH & TURBO → ULTRA-LOW, LOW, MID, HIGH & TURBO). The holster that we find inside the Nitecore E4K box is essential but well made. It is made of fairly soft cordura with a closure tore up. The central body of the Nitecore E4K has a non-slip diamond-shaped knurling while in the lower part we find fins of cooling that facilitate the disposal of the heat produced during the use of the E4K at the highest light levels.

There is a lot of great engineering in the Nitecore E4K, the unibody is rugged yet tactile, having been CNC machined from aluminium which makes it light, tough and able to dissipate heat well. It utilises 4 x Cree XP-L2 V6 LEDs for an impressive maximum output of 4400 lumens and a beam range of 211 metres on the turbo setting.

This light feels rather well balanced in a medium sized hand (not head/tail-heavy). Switching between overhand and underhand holding method is easy with its form factor. The knurling on the light enable it to be sufficiently “grippy”, even with wet hands/gloves. I want to clarify that the values expressed by the graphs must be taken, above all, as a reference because they are made with different means and environmental conditions This light REALLY puts out some lumens, if briefly. I like the big switch, too. I don’t care for the UI one bit, but this one’s recycled from another light where I didn’t like the UI, too. Long Review The Big Table Nitecore E4K Flashlight Before using the flashlight for the first time, remove the Insulation Film from the battery compartment. The light was subjected to warm water submersion, followed by cold water submersion and left under room temperature running water tap whilst running on HIGH.

The Solid RED indicator on the positive portion of the battery depicts charging in progress and Solid GREEN indicator on the positive portion of the battery depicts charging has completed. Paired with the included fast charging USB-C rechargeable 5000mAh NL2150HPR battery, this light can run for up to 30 days on ultralow mode, ensuring you have enough light for any activity. Use the included USB-C charging cable to charge the battery. sudden brightness that settles at 24 seconds on 3040cd. The autonomy with the 21700 5000 mAh battery is truly remarkable.Here’s a runtime on Turbo. Not that I want the light to cheat for specs, but I’d really like for the initial output to hold on just a little bit longer. At startup, it’s practically 5000 lumens! At… maybe 26 seconds, it’s around 4400 lumens. Then it falls right off.