Loop SK-01s LED Flashlight Review

The Loop SK-01s LED flashlight entered the market initially with a cool LEP, but the SK-01s is a LED flashlight! Same neat fidgety features. Read on!

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Official Specs and Features

Here’s a link to the Loop SK-01s LED flashlight product page.

Versions

Of just the Loop SK-01s LED flashlight there are a few versions – aluminum, and two titanium options. Of course, there’s a LEP version of the SK-01s, too.

Price

MSRP of the Loop SK-01s LED flashlight ranges from $219.95 as seen here, up to 379.95 for the titanium body version.

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Short Review

I think the Loop SK-01s LED flashlight is exactly what you’d expect it to be, and there are no surprises. That sounds unnecessarily bad, though – the features it purports to have are great, and work well! The light is precisely as fidgety as it needs to be. Only in a case or two do those features get in the way of using the light, but overall it’s good. As a flashlight, it’s good too!

Long Review

The Big Table

Loop SK-01s LED flashlight
Emitter:	Luminus SFT-40
Price in USD at publication time:	$219.95 through my affiliate link.
Cell:	1×18350
Runtime Graphs
LVP?	Yes
Switch Type:	E-Switch
Quiescent Current (mA):	?
On-Board Charging?	Yes
Charge Port Type:	USB-C (on cell)
Charge Graph
Power off Charge Port	–
Claimed Lumens (lm)	1600
Measured Lumens (at 30s)	1006 (62.9% of claim)^
Candela per Lumen	46.68
Claimed Throw (m)	500
Candela (Calculated) in cd (at 30s)	1355lux @ 5.855m = 46451cd
Throw (Calculated) (m)	431.0 (86.2% of claim)^
Claimed CCT	–
Measured CCT Range (K)	5900-7000 Kelvin
Item provided for review by:	Loop
All my Loop reviews!

^ Measurement disclaimer:  Testing flashlights is my hobby. I use hobbyist-level equipment for testing, including some I made myself. Try not to get buried in the details of manufacturer specifications versus measurements recorded here; A certain amount of difference (say, 10 or 15%) is perfectly reasonable.

What’s Included

• Loop SK-01s LED flashlight
• 1100mAh 18350
• Charging cable (USB to USB-C)
• Spare o-ring
• Spare washer
• Spare springs (3, 2 types)

Here’s a close-up of those springs and things.

Package and Manual

I gotta be honest here and say that the manual is no easier to read in person than it is in this scan. The font is tiny!

Build Quality and Disassembly

There’s a whole lot going on with the Loop SK-01s LED flashlight. It’s a flashlight. The head has a spinner. The body has a spinner loop that doubles as a sort of tactical grip. The body also has a slide with a fidgety switch that makes a great sound when released. There’s an indicating switch that has RGB. The front emitter area also has RGB. It’s a lot!

Still, it’s well-built. The “neck” spinner in particular really spins freely!

Again, on the body is this switch or latch. When released, the body slides up.

This extension is described as a mechanical lockout!

Sliding this body sleeve up makes the body longer but does not allow using longer cells like an 18500 or 18650. It does have the benefit of protecting the switch, though. So if you’re in a certain mode and don’t want that to changed, this is one way to sort of protect/prevent it.

Both head and tail have springs. The tail is an RGB e-switch, so a sleeve in the cell tube provides power back to the switch.

Size and Comps

107mm x 43mm and 242g.

If the flashlight will headstand, I’ll show it here (usually the third photo). If the flashlight will tailstand, I’ll also show that (usually in the fourth photo).

Here’s the test light with the venerable Convoy S2+. Mine’s a custom “baked” edition Nichia 219b triple. A very nice 18650 light.

Also above on the left is a new feature light!! Laulima Metal Craft sent this titanium Todai for some size comparison photos like the ones above. Laulima has bunch of incredible items. I’ve tested one (the Laulima Metal Craft Hoku) (the official site for Hoku is here) that was a Friend Fund Friday review. I was impressed enough by that Hoku that I bought a Laulima Metal Craft Diamond Slim (also in tumbled aluminum) (review is upcoming!) These lights by Laulima have impeccable build quality and not only that, they’re quite configurable. There are some (great, actually) default configurations, but Joshua Dawson (of Laulima Metal Craft) is open to ideas and emitter options and the like. I haven’t reviewed this Todai, but I have to say, it feels absolutely fantastic and I love it thus far. (Notably, I love how warm and eggy those emitters look through the TIR.)

Retention and Carry

Of all the features the Loop SK-01s LED flashlight offers, a great way to carry isn’t one of them. You’ll probably carry the light in a bag (loose?) until it’s needed, and then the most secure way to carry the light is to hold with the loop some way, like seen below.

There’s no pocket clip or holster.

Power and Runtime

Loop includes an 18350 for powering the SK-01s. It’s a button-top, 1100mah 18350.

The cell goes into the light in the usual way: button top (positive) toward the head.

In case you forget that, you can reference the icon inside the cell tube:

Below are a few runtime tests. Performance is pretty good, but the modes don’t seem to be held steadily – they trail off during their use. That’s not a huge surprise, nor is it the worst feature of any flashlight.

Low voltage protection is observed, with the light shutting off at around 3V. The manual supports the idea that the tail RGB can indicate approximate cell voltage, but I’m not sure how it works. The manual states “depends on Tail Ambient Light.” and I can’t make it make sense in use.

Charging

While the SK-01s itself doesn’t offer charging, the included 18350 does. There’s a USB-C charging port on the positive end.

A charging cable is included. It’s USB to USB-C.

Charging works fine, and is quick. The rate is over 1C! That’s quick!

While charging, an indicating LED on the 18350 responds as follows:

Red: charging
Blue: charging complete

Modes and Currents

Mode	Mode Claimed Output (lm)	Claimed Runtime	Measured Lumens
Turbo	1600	30s+1h	1322 (0s) 1006 (30s)
High	600	1h5m	367
Low	150	3h35m	128
Eco	5	16h	2.2

Pulse Width Modulation

The lowest and highest mode do not have PWM, but the middle two seem to.

Here you can see a “baseline” – a chart with almost no light hitting the sensor. Then there’s the Ultrafire WF-602C flashlight, which has some of the worst PWM I’ve seen. It’s so bad that I used a post about it to explain PWM! Here are multiple timescales (10ms, 5ms, 2ms, 1ms, 0.5ms, 0.2ms) to make comparing this “worst” PWM light to the test light easier. That post also explains why I didn’t test the WF-602C at the usual 50us scale.

User Interface and Operation

A single switch is used for operating the Loop SK-01s LED flashlight. It’s an e-switch but set up a lot like a mechanical switch.

There’s a neat ruby-like inset inside the metal rim. It’s a very cool switch.

The action is very low.

The switch has a red ruby but also RGB functions. The red resting state doesn’t seem to flavor the RGB, though (not sure how that works!). As far as I can tell from using the light and reading the manual, the action that selects the front RGB option (of which there are 12) is the same action that sets the tail switch RGB (of which there are 5 options.) This means that the two aren’t tied together and that getting one to match up with the other will be possible… at least once. It’ll be hard to cycle through the options to match them, though, since going through all 12 front RGB options will cycle the tail options over twice. Maybe there’s something I’m missing in the manual, though. In any case, matching them hasn’t been something I cared about, so I wouldn’t call this a big deal.

Here’s a user interface table!

State	Action	Result
Off	Click	On (Mode memory of high/low)
Off	Hold	Eco
On	Click	Off
On	Hold 1s	Iterate High/Low
Off	Hold 2s	RGB on (mode memory of front and switch (separately)
RGB	Hold	RGB for front 12 modes and tail RGB 5 modes advance (separately!)
Any	Double click	Turbo
Any	Click 3x	Strobe
Off	Click 4x	Lockout
Lockout	Click 4x	Unlock
Lockout	Click	Iterate RGB on (both head and tail)^
Lockout	Hold	RGB for front 12 modes and tail RGB 5 modes advance (separately!)^

^ I can’t see where the manual covers RGB during lockout. It’s not much (if any) different from RGB during unlocked, but no white modes are available.

LED and Beam

Loop used a Luminus SFT-40 emitter in the Sk-01s. That emitter is coupled with a TIR and provides a throwy beam.

Interestingly (or “awesomely”) the front emitter (“emitters” really) shines through these little gaps in the head, just above that spinner.

The bezel has glass-breaking balls and a relief too, so light escapes when headstanding.

As I said above, the front offers RGB. Not just RGB though – there are modes!

LED Color Report (CRI and CCT)

CRI and CCT reports are shown for only the white output. There are four modes. CCT is cool to very cool (on Turbo) and CRi is low. This is to be expected, and seems somehow excusable in a light with such a … tactical … look? feature set? I don’t know. But it seems ok.

Beamshots

These beamshots always have the following settings:  f8, ISO100, 0.3s shutter, and manual 5000K exposure. These photos are taken at floor level, and the beam hits the ceiling around 9 feet away.

Tint vs BLF-348 (KillzoneFlashlights.com 219b version) (affiliate link)

I keep the test flashlight on the left and the BLF-348 reference flashlight on the right.

Above are the white modes. Below are just a random smattering of RGB options, all of which are fairly low output in actuality.

Here’s what the beam profile looks like from the color modes. One thing that’s nice (and doesn’t come across great because of the 219b comparison) is that the RGB output are symmetrical (despite being highly shaped.)

I compare everything to the KillzoneFlashlights.com 219b BLF-348 because it’s inexpensive and has the best tint!

Conclusion

What I like

• So many fidgets
• The neck spinner spins very freely!
• Mechanical extension/lockout releases with a very resounding and pleasant “thock”
• 18350 is included
• 18350 is standard
• USB-C charging works well
• RGB emitter options in the head are fun
• RGB options in the tail are neat!
• Tritium slots

What I don’t like

• Tail RGB and head RGB are coupled, but not aligned
• There’s a lot going on with the light (I usually say this like “It’s very active in the hand.”)
• Extension makes you hope for 18650 support, but that’s not what it is
• Fairly costly

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Notes

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