[Review + Videoreview] Sofirn SD05 (21700, XHP50.2, diving flashlight)

Here is my review of the Sofirn SD05. It includes a written review as well as a video review.

The flashlight has been provided by Sofirn for review. Thank you, Sofirn!

Purchase links (non-affiliate)

Aliexpress: Sofirn SD05

Sofirnlight: Sofirn SD05

Amazon DE: Sofirn SD05

Amazon IT: Sofirn SD05

Banggood: Sofirn SD05


The Sofirn SD05 is a true diving flashlight, made for underwater use down to 100m. It is slightly different than normal flashlights because it has a magnetic control ring instead of a switch and double o-rings for absolute waterproofness. With a XHP50.2 and a 21700 battery the Sofirn SD05 will be capable to offer a decent brightness with long runtime.
The Sofirn SD05 is the first real diving flashlight I own. I am not a diver but I may try to perform an underwater test in a lake in the summer and add that later. Meanwhile I will use it like a normal flashlight with excellent watertightness.

Here is the video review of the Sofirn SD05. If you prefer the written review, please continue reading below.


What is included

- Sofirn SD05

- 21700 4000mAh Sofirn battery

- Manual

- 18650 adapter sleeve

- Charger single slot

- Micro USB cable

- Lanyard

  • Spare o-rings


The manual

The manual comes in English, German and Russian(?).


Tailcap current (ampere draw)

Low: 0.45A
Med: 1.40A
High: 5.86A

The Sofirn SD05 uses a boost driver which draws twice as much current as the led gets. The boost driver steps up the voltage from 3V to 6V so that the current gets divided by two. If you don’t consider the efficiency of the driver and the losses in the circuit the XHP50.2 gets 0.23A on low, 0.70A on medium and 2.93A on high. The XHP50 is rated for a maximum current of 3A so it is driven within the specs.


XHP50.2 6500K in an orange peel reflector

The threads at the tailcap are deeper and square cut while the front threads are smaller and not square cut (front/head threads on the left, tail threads on the right). Apparently the SD05 should be unscrewed only at the tail to change the battery.

Purple AR-coated glass lens

Battery and charger

I have charged the Sofirn 21700 4000mAh battery in my Miboxer charger with 0.5A from the 3.5V it came with to 4.2V and it showed 3620mAh. Considering it is the first charge and from 3.5V instead of 3.2-3.3V it should certainly reach the rated 4000mAh.

The 31 Milliohms internal resistance will be a bit lower than the charger displays it. It is about the same value of my black 26650 Liitokala so the 21700 Sofirn cell should be capable of 20-25A. No clue why they wrote 40A on the cell, that must be the absolute peak current value for something like five seconds. The internal resistance is lower than the 21700 4800mAh 15A Tesla cell on its right in the Miboxer charger but not as low as a Samsung 30T.

The included single slot 0.7A USB charger is simple but reliable. The led shines red when charging and switches to green when the battery is full. It is a solid charger and not as cheaply made as most other generic chinese chargers. For those who don’t charge many lithium batteries and don’t need fancy current adjustments and different values displayed it will be a handy charger.


The Sofirn SD05 with its siblings: 21700 Sofirn battery, Sofirn SD05, Sofirn SP31 V2.0, Sofirn C8F

Here is the Sofirn SD05 compared to some famous flashlights: Sofirn SD05, Convoy S2, Fireflies E07, Lumintop BLF FW3A copper, Convoy C8






Sofirn SP31 V2.0

Sofirn C8F with 3 XPL HD 5000K

Astrolux FT03 with SST40 5000K


Teardown and internals

You shouldn’t disassemble your flashlight like I do here as it voids the warranty and it may damage your flashlight. I’m showing the teardown and internal parts here so that you don’t have to unscrew the flashlight yourself risking to ruin it. Of course, this does not apply to all experts and modders around here.

The driver seems to be glued in and I didn’t want to break something so you can see it only from the back.


Even though I never used it for diving I would consider the Sofirn SD05 well suited and usable for underwater tasks. It is compact enough to be held in one hand and the magnetic control ring turns easily with a firm click at the mode positions. It seems you could even use it with gloves.
So far I did not perform an underwater test for waterproofness but judging from the double o-rings, tight and lubed threads, a magnetic control ring and the thick glass lens I assume the water will have no chance to leak inside the Sofirn SD05.
The Sofirn SD05 is another top-notch built flashlight from Sofirn that has all necessary features for a diving flashlight. Therefore, I would definitely recommend it to the divers, the people living in very rainy areas and to those who commonly drop their flashlights in lakes. :wink:

What I like

- Compact and sturdy flashlight, suitable for one-handed operation

- Double o-rings on both ends of the battery tube and under the glass lens at the front

- Simple magnetic control ring with three modes, from low to high

- 21700 cell format gives long runtime for a still pocketable flashlight format

- Usable underwater up to 100m deep (not tested but I would never dive that deep)

- Slightly glossy black anodizing, square cut threads at the tail, thick AR-coated glass lens

  • Good 21700 battery included, charger and 18650 adapter supplied as well

What could be improved

- I would love a 4000K or 5000K NW version or maybe even a 80 or 90CRI led.

  • The flashlight steps down after 3 min on high mode. A forth mode between med and high would be useful here for extended runtime with decent brightness, using 3A maybe and lasting for over an hour.

Thank you all for reading my review and/or watching the video review. :slight_smile: For any questions or suggestions please feel free to ask and comment below.

A true underwater test will be added below when I find some time and the right location in the summer.


Excellent review!

Love this light. I use it quite a bit around the house and garage. Should also make a good muggle light to lend out, or gift.

I, too, wish it had a forth brightness level. One slotted in between medium and high. That’s about it for negatives, for me.

If I get to South East Asia this summer, I will takes this torch snorkeling and diving in the sea.

Thanks Swabs.

I guess the Sofirn SD05 would look awesome underwater with a 90CRI led.

It seems there is a new version without 3 min stepdown.


I suppose there’s no single high-CRI LED in the same league as the XHP50.2 as used in the Sofirn SD05….

which is probably why they have the Sofirn DF10, which uses the single LH351D 5000k 90CRI (~1000 lumens) and the Wurkkos DL40 with 4x LH351D 5000k 90CRI (“5000” lumens). Wurkkos appears to be affiliated to Sofirn.

Cree produces the XHP50.2 and XHP70.2 in high-CRI versions. Compared to the 70 CRI leds they are slightly more yellow or green and have lower bins. The color rendering is great, though.

You are right, d_t_a, the Wurkkos DL40 is definitely worth considering if you want maximum color fidelity and brightness when diving. The Sofirn DF10 is nice as well.

Sofirn is the factory that produces the Wurkkos flashlights. Apparently they have been allowed to sell the Wurkkos flashlights also in their Aliepress store.

Could anyone confirm the ANSI measurement of the spare O-rings? Thanks!