The Nitecore T4K is part of Nitecore's T-series and is a very compact and extremely powerful keychain flashlight. The T4K delivers 200 lumens on its highest brightness setting and an impressive 4000 lumens in turbo mode. However, this output is only available for about 10 seconds. The turbo mode can be activated multiple times. The integrated Li-Ion battery with a capacity of 1000 mAh is charged via a USB-C port. The OLED display provides various information, such as battery level, selected brightness level, mode, or remaining runtime.