Review Nitecore SRT6i - Smart Selector Ring

Newly Enlightened
Dec 3, 2012
NITECORE SRT6i was sent to me directly from Nitecore for review.


For technical details and to purchase the torch: ... -srt6i.htm(link is external)

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After a few years Nitecore presents a new product of the SRT series (SmartRing Tactical Series), the SRT6i.

The Nitecore SRT6i, with the fourth generation of the SSR (Smart Selector Ring), adopts a rotating ring, now positioned at the tail, which allows a quick and precise selection of the desired level in addition to the lockout mode. So through the ring we can quickly select the 3 available levels in addition to the lockout mode and the tactical mode (TAC Mode).
This solution makes it really easy to use with one hand by changing the brightness with a simple rotation.
Nitecore SRT6i also adds to these features the new dual-stage tail button which allows, pressed halfway or fully, two different types of selection. The SRT6i is also equipped with "STROBE READY" technology with fast activation of the Strobe.

SRT6i uses a high performance LED (according to the user manual, they later confirmed to me that it is a CREE XHP35 HI) with a maximum output of 2100 lumens and a maximum peak beam intensity of 65,200cd with a maximum throw of 510 meters.
SRT6i is sold with a 5000 mAh lithium battery in 21700 format ("i" series) and is rechargeable via the USB-C port with a maximum autonomy of 70 hours. The SRT6i can also be powered by two CR123/RCR123 batteries via the adapter (not included in the package).
Nitecore SRT6i has 2 switches, both in the queue, with 3 light levels (besides the strobe). It has an IP68 waterproof rating (2 meters submersible) and has shock resistance up to 2 meters.
SRT6i is compatible with already available optional tactical accessories such as, for example, the TSL10i tail cap with signaling LED and the RSW2i remote control, and is particularly recommended for law enforcement, assault operations, self-defense, search and high-risk patrols.


* TURBO runtime is tested without temperature adjustment.

  • Dual tail switches enable intuitive operations, specially designed for law enforcement, hunting and tactical applications
  • 4th generation of the world's first SSR (Smart Selector Ring) Technology for smoothly and rapidly selecting brightness levels and modes
  • Utilizes a high performance LED with a max output of 2,100 lumens
  • An optical system combined with crystal coating and "Precision Digital Optics Technology" (PDOT)
  • Max peak beam intensity of 65,200cd and max throw of 510 meters
  • Max runtime of 70 hours
  • 3 brightness levels, lockout mode and TAC mode available
  • STROBE READY™ Technology to enable a quick access to STROBE Mode (Patent No. ZL201320545349.4)
  • Equipped with a power indicator
  • Intelligent Li-ion battery charging circuit with a USB-C port
  • NITECORE 21700i Li-ion battery included (NL2150HPi 5,000mAh) • Highly efficient constant current circuit provides a stable output
  • Incorporated Advanced Temperature Regulation (ATR) module (Patent No. ZL201510534543.6)
  • Strike bezel uses high strength silicon nitride ceramics to enable excellent glass breaking performance
  • Optical lenses with double-sided scratch resistant coating
  • Constructed from aero grade aluminum alloy • HA III military grade hard-anodized finish
  • Waterproof and dustproof rating in accordance with IP68 (2 meters submersible)
  • Impact resistant to 2 meters

Length: 163mm (6.42") Head Diameter: 40mm (1.57") Tube Diameter: 25.8mm (1.02") Tail Diameter: 31mm (1.22") Weight: 167g (5.89 oz) (Battery Not Included)

Any DOA / defective product can be replaced through a local distributor / dealer
within 15 days of purchase. After that, the defective or malfunctioning product can be repaired free of charge within 60 months from the date of purchase. Beyond 60 months, a limited warranty applies which covers the cost of labor and maintenance, but not the cost of accessories or replacement parts.

Nitecore SRT6i arrives in a dark colored cardboard box with the classic writings that show the main characteristics that distinguish it. Inside the package we find, in addition to the Nitecore SRT6i with the 5000 mAh 21700 lithium battery (NL2150HPi), the Clip, the USB-C charging cable, the holster, the lanyard, a spare O-ring, manual and guarantee.



The stainless steel Clip, included in the package, allows easy insertion into jeans. Inserted near the tail cap, it remains firmly in place thanks to the slots on the torch body and the block made by the tail cap. Put in this way, the Clip can only be removed after removing the tail cap. Great solution.


Nitecore SRT6i has good build quality, there are no strange edges or construction residues. It is made of aluminum alloy with an anodized finish, glossy black, military-grade hard. In the hand it holds well despite the not exactly small dimensions (163mm) and the weight of 248g with the battery and Clip inserted.
Thanks to the shape of the head and tail, the SRT6i does not slip easily once placed on a table.




On the head of the SRT6i we find a deep projector with a SMO dish with the CREE XHP35 HI LED in the center. Thanks to the PDOT treatment (Precision Digital Optics Technology) the beam is optimized for a more uniform beam while the optical lenses have an anti-scratch coating on both sides and an anti-reflection.
With this LED, Nitecore SRT6i, reaches the maximum brightness of 2100 lumens and covers a distance of over 510 meters.


The hardened steel bezel has 3 high hardness silicon nitride ceramic balls which enable quick and easy operation for self-defense such as breaking glass. The smooth surface of the balls prevents accidental scratches on your clothes or backpack.


Laterally, above the head, there is the charging socket in USB-C format protected by a thick rubber cap but easy to lift thanks to the recess under the flap.

In my tests I used about 3h45min to fully recharge the supplied battery.


The central body of the Nitecore SRT6i has a rhomboid-shaped non-slip knurling and two spaces that offer the possibility of inserting accessories such as the TacticalRing Pro NTR10. The thicknesses are good and the lettering is clearly legible.

The threads on the torch body to screw the tail cap arrive well greased. They are anodized and therefore, by partially unscrewing the tail cap, they allow the mechanical locking of the torch. There is an O-ring to seal against water and dust. Nitecore SRT6i is IP68 certified (2 meters submersible).

At the two poles, for contact with the battery, we find a system of plated button contacts at the tail while at the head a system composed of plated rings and spring.


The battery to operate the SRT6i is a protected Nitecore 21700 (NL2150HPi 5.000 mAh 15A) of the "i" series.
NL2150HPi is a proprietary 21700 rechargeable Li-ion battery with dual-way output with positive and negative polarity on both ends with a high energy and density.

The only unscrewable part of the SRT6i is the tail cap. On the tail cap we find the fourth generation Smart Selector Ring (SSR). The rotating ring, positioned at the end, allows quick selection of one of the three available levels marked by a number; LOW (1) of 30 lumens, MID (2) of 300 lumens and TURBO (3) of 2100 lumens. In addition to changing brightness, by turning the ring, it is possible to select the lockout mode to inhibit both buttons (Lockout mode) or the tactical mode (TAC mode) for quick access to LOW or TURBO levels.


On the tail cap there are two electronic switches; Power Button and MODE Button.
The round-shaped power switch, Power Button, is raised above the MODE button. This allows you to find it easily in the dark. The Mode Button (dual stage) has a double function if pressed halfway or fully. Furthermore, the MODE button is slightly raised and not flush as, for example, on the P20i. This will make its activation easier and faster. The two switches of the SRT6i are, for me, the best implementation found so far, regarding the tail buttons, on Nitecore's tactical flashlights.


Nitecore SRT6i near to other flashlights and the previous SRT7GT.


From left: Battery Nitecore NL2150HPi, Nitecore P20i, Cyansky K3 v2, Nitecore SRT6i, Acebeam X80 e Fenix TK11TAK.



Nitecore SRT6i
has two tail switches and 3 brightness levels in addition to the special STROBE mode (STROBE Ready).

o Low: 30 lumens / 70 hours / 56 meters
o Mid: 300 lumens / 7 hours and 30 minutes / 175 meters
o Turbo: 2100 lumens / *30 minutes / 510 meters
o Strobe: 2100 lumens

* The operating time of TURBO is tested without temperature regulation.


Momentary tactical illumination
Brightness level 1-3: When the light is off, half-press the power button to turn it on momentarily. Release to turn it off.
TAC mode
  • Press and hold the power button halfway to momentarily enter the LOW level. Release to turn it off.
  • Press and hold the power button fully to momentarily enter the TURBO level. Release to turn it off.

Turning on and off
Brightness level 1-3:
  • When the light is off, fully press the power button to turn it on.
  • When the light is on, press the power button all the way down to turn it off.

Selecting the brightness level or mode
When the light is on, rotate the smart selection ring on the end of the flashlight to select a brightness level/mode.
  • Rotate the smart dial clockwise from far right to left to cycle through the following brightness levels/modes: TAC - TURBO (3) - MID (2) - LOW (1) - Lock Mode.
  • These brightness levels/modes can be used in reverse by turning the Smart Selector bezel counterclockwise.
  • When you rotate the Smart Selector bezel in Lockout mode, both buttons are locked and are unavailable to turn on the flashlight.

Direct access to TURBO
  • When the light is off, half-press the MODE (STROBE READY™) button to access TURBO. Release it to turn it off.
  • Brightness level 1-2: When the light is on, press and hold the MODE button halfway (STROBE READY™) to enter TURBO. Release to go back to the previous state.
Note: TURBO level produces strong heat when activated for long periods and the flashlight automatically reduces some lumens to avoid overheating and extend battery life.

  • When the light is off, long press the MODE (STROBE READY™) button to enter STROBE mode. Release to turn it off.
  • Brightness Level 1-3: When the light is on, fully press the MODE (STROBE READY™) button to enter STROBE mode. By briefly pressing the MODE button (STROBE READY™) to return to the previous state or by turning off the flashlight, you can exit the STROBE mode.

Power indication
  • When the light is on and the remaining battery power is approximately 50%, the power indicator flashes every 2 seconds to inform the user.
  • When the light is on and the battery is low, the power indicator flashes rapidly and continuously to inform the user.


The beam
of the Nitecore SRT6i has good uniformity with a pleasant tint and no visible artifacts. With the lighting test near the wall, a bright white spot is noticed while the crown that surrounds it is tending towards yellow. The particular geometry at the edges of the spill is also visible, which does not disturb the outdoor lighting.


Nitecore SRT6i, with narrow angle side lighting, is a flashlight made to illuminate from a distance. I can't see any significant PWM in any of the three modes by eye. The beginning of the spill from the walk is about two meters.


Below the wall test of the beam of the Nitecore SRT6i together with the Nitecore P20i.


The CCT (color temperature) and Ra (color rendering) values taken with OPPO's Light Master Pro, two meters away from the sensor, vary according to the selected light level.
LOW level 30 lumens, CCT= 5873 - Ra= 71.6
MID level 300 lumens, CCT= 5897 - Ra= 71.8
TURBO level 2100 lumens, CCT= 6438 - Ra= 73
The calculated Duv with the brightest level is 0.0036.


The peak values in candela (cd) taken with the Luxmeter at 10 meters are higher than those declared by Nitecore.

LOW = 1223cd
MID = 12796cd
TURBO = 77718cd


With a thermal imaging camera I detected how the heat is distributed on the flashlight in TURBO mode at 2100 lumens after 1min30sec, 10min and 20 from switching on. The photos were taken during the runtime test breezy. No heat problems holding the Nitecore SRT6i in hand.


The Runtime were done in a closed environment with a temperature of about 16°C using the supplied fully charged Nitecore 21700 5000 mAh battery.

I would like to clarify that the values expressed by the graphs must be taken, above all, as a reference because they are made with means and environmental conditions different from those used in the laboratory.

The discharge times (runtime) indicated by Nitecore are 30min for the Turbo measured without intervention of the ATR module and 7h30min for the medium level of 300 lumens.
While the regulation of the medium level (300 lumens) is flat until it drops after 370 minutes from switching on and switches off after more than 8 hours, that of the brightest level, turbo 2100 lumens, has an initial rise and a sudden descent after one minute of work. Subsequently, after about 130 minutes, there is another rapid ascent and descent before the decrease in light which settles at the average level for about 16 minutes and then quickly descends again due to battery depletion.
The test done in turbo mode with assisted ventilation clearly shows the adjustment of the Nitecore ATR module based on the temperature.



VIDEO Review

FINAL CONCLUSIONS: The new Nitecore SRT6i is a purely tactical flashlight equipped with the fourth generation of the SSR (Smart Selector Ring). The selector ring is located, in this new product, on the tail cap and allows a simple selection of one of the 3 available levels in addition to the flashlight lockout and tactical mode (TAC). This new selector, combined with the new dual-stage "mode" button in the queue, makes the use of the SRT6i simple and fast, making it one of the best creations made by Nitecore on tactical flashlights. Nitecore SRT6i offers rapid activation of Low, Turbo and Strobe modes (Strobe Ready) with a maximum brightness of 2100 lumens and a beam that reaches a maximum distance of 510 meters. There are three levels of light available to which perhaps I would have added a high level of 1000 lumens. Finally, the sales package is complete with Clip, Case and Battery to be able to use the flashlight immediately. Thanks for reading the review.


Flashlight Enthusiast
Jan 5, 2009
Nice review thanks 🙏 Fenix have a similar system but it harks back to my ten year old thrunite scorpion and the gladius before that . Sometimes they just go around in circles reselling ideas . Nothing new here apart from some power.