Cyansky P20

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Cyansky P20 review

Cyansky P20 specifications

Brand/modelCyansky P20
LEDLuminus SST-40
Lumens1600 Lumens
Beam intensity14405 cd / 240m
Battery config.1*18650 / 2*CR123A
ReflectorLight orange peel (LOP)
Review dateApril 2021


A bit of a surprise review, this one. Freasygears sent us the Cyansky P20 in the same package as their H3 to review.
The P20 is a fairly standard-looking 18650 light. Just like the H3 is the baby brother to the H5, so the P20 is to the Cyansky P25. Both the P20 and P25 are dual switch straight tube lights but the P20 swaps the massive XHP70.2 LED for the SST-40 and makes a few other changes too.

Package quality.

Cyansky used a folded plastic box for the P20. The back of the box includes the specs and also includes a crude runtime diagram. I wish more manufacturers would do this, as it shows the step down from turbo and gives a good overview at a glance.

  • Cyansky P20
  • 18650 cell
  • Holster
  • Clip
  • Lanyard
  • Spare O-ring
  • Spare rubber switch boot
  • Manual
  • Micro USB cable

Flashlight in use

The P20 is a fairly standard straight-tube tactical light, so will be pretty much what you’d expect. It’s quite long but it doesn’t feel too big and the 2 switches are easy to reach. The P20 has a mechanical forward clicky switch at the tail and an e-switch on the side. The e-switch is the same style as the one found on the Cyansky P25.

Lots of the detailing is different between the P20 and P25 and at a glance, you may think they were made by different manufacturers. For example, unlike the P25, the P20 will roll without the clip and won’t tail stand at all.

The clip is short relative to the P20’s length but is strong and works fine. If you want better retention, there’s always the included holster, with velcro and a belt loop. The holster is reasonable quality and fits the light well, even with the pocket clip attached.

The other retention option is the lanyard. This is the most fancy lanyard I’ve seen with a flashlight and puts all the other lanyards I have to shame. The lanyard is a challenge to thread through the holes but once that’s done it feels very secure.

Build Quality, and Warranty

There’s not really knurling on the P20 but it does have rings, similar to heat fins around the head and tail. The aluminium anodising is shiny and smooth. The tailcap spring appears beefy enough.

The threads on the tail end are smoothly square cut and anodised, so you can lock out the light with a quarter turn. The head end didn’t easily unscrew and appears to be glued – Cyansky doesn’t intend for you to remove it here.

There’s no spring on the head end but instead there’s physical reverse polarity protection.

Freasygears / Cyansky provide a 5 year warranty, where they’ll repair or provide a replacement if the flashlight fails due to material or workmanship

LED, Lens, Bezel, and Reflector

I can’t copy anything from the Cyansky P25 review here, as the LED is completely different. The P20 uses a cool white Luminus SST-40 LED. Whilst it’s not too cool, the tint is noticeably yellow/green, mostly at the low levels.

The Cyansky P20 reflector is orange peel but smoother than the P25. This, along with the smaller LED, helps the P20 throw further. This results in 9 lm/cd, allowing it to throw further than the bigger P25 with half the lumens.

Dimensions and size comparison

  • Length: 13.41 cm / 5.28 inches
  • Head diameter: 2.55 cm / 1.00 inches
  • Body diameter: 2.19 cm / 0.86 inches


  • With cell: 128 g / 4.5 oz
  • Without cell: 79g / 2.8 oz

EDC / Tactical Flashlight comparison

Similar EDC / tactical lights compared.

From left to right: Convoy S21B, Sofirn SP31, Cyansky P20, Generic X800 zoomie, Cyansky P25, Cyansky H3.

Driver & User Interface:

The P20 has 2 switches: a forward clicky mechanical switch at the tail and a side e-switch.

The tail switch only turns the light on and off. Being forward clicky, you can half-press for momentary-on before the switch clicks into place. This makes the flashlight good for very precise timing control, such as for using with a weapon or signalling Morse code. The light has mode memory, so there’s no way to change modes with the tail switch.

The e-switch changes modes and doesn’t allow turning the light off.

Modes: Low, Medium, High, Turbo, Strobe

From OFF:

  • Half press tail switch: Momentary on
  • Press tail switch: On
  • E-switch: nothing

From ON:

  • Tail switch: off
  • Click: Next mode (L-M-H-T, then back to L)
  • Hold: strobe

Mode memory:

  • Yes

Low voltage warning:

  • Yes


  • Strobe cycles between a fast and slow frequency. Strobe isn’t memorised.
  • Click e-switch to go to last mode


  • I couldn’t detect PWM on any modes.

Batteries & Charging

The Cyansky comes with a rechargeable 18650 cell, rated at 2600 mAh. The cell includes a Micro USB port for charging and red/green indicator light. The indicator turns green and the cell stops charging at 4.21V. I measured 2491mAh going into the cell. 2600 mAh is on the low end of capacity these days, even for high drain cells. You can also charge the 70.1mm long cell in a normal li-ion charger.

The Cyansky P20 has physical reverse polarity protection, which means that button cells are needed. A 64.7mm flat top didn’t work at all but a 66.5mm button top cell was fine. Stick to button top cells for best results.

Cyansky states that you can also use a pair of CR123A or 16340 cells but I didn’t have any to test.


Lux meter: All lux and lumen measurements are from my home made integrating sphere, calibrated with a range of factory specced lights. Measurements are done with a UNI-T UT383S lux meter and Adafruit TSL2591 connected to a Raspberry Pi (using RuTiTe by bmengineer). Expect them to be within +/-10%.

DMM: Current readings were taken with a Precision Gold PG10B DMM, all with the cell charged to 4.22V.

Measurements here are for the white mode, without any filters. 

I used Cyansky’s provided 2600mAh 18650 cell for all measurements. Current readings were taken with a Precision Gold PG10B DMM, all with the cell charged as much as it would take (4.21V).

Amp and lumen measurements

When taking current measurements on turbo, the H3 seemed to notice the increased resistance from the wire and dropped immediately to 1 or 2A.

ModeCurrent (A)Spec (lm)Measured (lm)
Low0.01A10 lm11 lm
Medium0.34A200 lm229 lm
High1.29A650 lm710 lm
Turbo (0s)4.06A1740 lm
Turbo (30s)1600 lm1665 lm
Turbo (10m)913 lm

Runtime graph

On turbo the P20 starts off at 1740 lm. At 30 seconds I measured it as 4% over spec at 1665 lm. Most of the other Cyansly lights I’ve reviewed have been either on spec or very slightly under. You can see that the P20 drops down over the first 3 minutes to about 900 lumens, then holds that level for 1 hour 8 minutes. It then steps down to the high level for a few seconds, then down to medium for 4 minutes. After 45 minutes on low (2 hours total) the LVP kicked in and the light turned off, with the cell at 2.75V. I think an hour of 900 lumens is pretty good for an 18650 light, especially with a 2600 mAh cell. Stick a 3600mAh cell in and you should get over 90 minutes runtime.

The high mode doesn’t really drop down at all and sustains around 700 lumens for 1 hour 50 minutes. Medium lasted 6 hours 33 minutes at about 230 lumens.

Throw numbers:

The throw numbers I got for medium, high, and turbo were all about 20% over the spec, which was a surprise as my numbers for their H3 were within 3%. 300m throw is much throwier than their P25 and makes a very useful beam.

Low19m / 90 cd19m
Medium85m / 1801 cd104
High153m / 5852 cd186
Turbo (0s)300m
Turbo (30s)240m / 14405 cd295m


Photos were taken with a Pixel 3a, set to 1/2s shutter speed and ISO 400, F1.8. White balance was locked on cool white.

Distance to the bench is 6m, tree on the right is 13m, tree on the centre right is 18m and the building behind it is 69m.

  • Convoy S21B
  • Cyansky P20
  • Cyansky P25
  • Emisar D4V2 (XPL-HI)
  • Lumintop D1
  • Sofirn SD05

Disclaimer: This flashlight was sent to me for review at no cost by Freasygear. I have not been paid to review, nor have I been holding back on problems or defects.

Explanation on star ratings:

  1. – Avoid: my phone flashlight would be a better choice
  2. – Poor: significant defect or issues, much better options available at the same price
  3. – Average: some defects or issues
  4. – Good: recommended (minor issues)
  5. – Great: highly recommended

Final Verdict


  1. Built in charging
  2. Good, stable runtime
  3. Comes with lots of accessories and spare parts


  1. No moonlight mode
  2. Doesn’t tail stand
  3. Micro USB instead of USB-C (but I guess that’s still better than no built in charging)
  4. Slightly green tint
Reviewer Dave
Author: Dave

4 stars: ★★★★★

I couldn’t really fault the larger P25 but although they’re very similar, I’m finding the P20 not quite up to scratch. Maybe it’s the tint or maybe I’m just expecting more output on turbo from an 18650 flashlight. That’s probably my fault for chasing after lumens.

Both the P20 and the bigger P25 are good lights but the P20 only really seems worth buying over the P25 if you want something more compact.

Aside from the size, the main difference is the beam profile and output. The P20 is only slightly more throwy (240m vs 192m) but the P25 is about twice the lumens (3000 lm vs 1600 lm). This results in a fairly normal 9cd/lm for the P20 and a floody 3cd/lm for the P25.

As with all the other Cyansky lights I’ve reviewed, I’ve been impressed with the runtime too.

The Cyansky P20 gets 4 stars and I’d recommend it if you’re after an 18650 flashlight that’s slightly tactical: the UI is straightforward and the flashlight seems solidly built.

Cyansky P20 for Sale

1lumen selects and reviews products personally. We may earn affiliate commissions through our links, which help support our testing.