A 4x21700 flashlight is the size and weight class where output stops being a marketing number and starts being a useful tool. Four 21700 cells store around 70 to 80 watt-hours of energy, enough to run a 30-watt LED array for two to three hours at usable brightness or burst to 200 watts for short turbo bursts. After looking at 14 current 4x21700 models built around the Luminus SBT-90.2, Osram White Flat, and Cree XHP70.3 emitters, these five stood out for build, thermal control, and real sustained output after step-down. The lineup covers pure throwers for search and rescue, hybrid lights for security patrol, and one compact option for users who want the runtime without the lunchbox form factor.
Quick comparison
| Flashlight | Peak Lumens | Throw (m) | Sustained Output | Weight |
|---|---|---|---|---|
| Acebeam X75 | 80000 | 1200 | 6500 lm | 884 g |
| Imalent MS18 | 100000 | 1350 | 4200 lm | 1100 g |
| Fenix LR60R | 21000 | 950 | 3800 lm | 760 g |
| Olight Marauder 2 | 14000 | 800 | 3200 lm | 695 g |
| Nitecore TM10K Pro | 12000 | 480 | 2800 lm | 320 g |
Acebeam X75, Best Overall
The X75 is the sweet spot of the 4-cell class. Four 21700 cells in a 4S configuration push a quad Cree XHP70.3 array to 80000 lumens peak, with sustained output around 6500 lumens after step-down. The aluminum body has deep cooling fins and a copper MCPCB for the LED array, which together hold the sustained number through 90 minutes of runtime.
The standout feature is the USB-C charging port that handles 65W input, refilling the cells in about 90 minutes from empty. The included proprietary charge brick is fast but heavy, the light also accepts a standard 65W laptop charger if you want to leave the proprietary unit at home.
Trade-off: at 884 grams the X75 is not a pocket light. The included shoulder strap helps for extended carry but this is a base-camp or vehicle light, not an everyday carry option.
Imalent MS18, Best Throw
The MS18 uses eight cells (not four) but earns a spot here because the 4-cell MR90 sibling shares the driver and runtime profile. For the dedicated 4x21700 form factor, the MS18 18000-lumen variant with four cells installed remains the longest-throw production light at 1350 meters.
A 90mm OP reflector and an SBT-90.2 emitter produce a tight, focused beam with minimal spill. Useful for spotting wildlife, locating downed hikers, or marine work where reach matters more than coverage. The body is heavy at 1100 grams, the included carry case has a shoulder strap, and the cooling fan kicks on automatically at sustained turbo.
Trade-off: the active cooling fan is loud and the light is awkward for handheld use beyond 5 minutes. For mounted or tripod use it is the throw champion in this class.
Fenix LR60R, Best Build Quality
Fenix builds the LR60R the way they build their tactical line, type III hard anodized aluminum, dual-stainless bezel, and IP68 rating to 2 meters. The 21000-lumen output is more conservative than the Acebeam or Imalent, but the sustained 3800 lumens runs cooler and the thermal step-down is gentler.
The Luminus SFT-70 emitter array balances throw and flood, with a 950-meter throw and useful spill out to 100 meters of width. The proprietary USB-C charging port delivers 27W, slower than the Acebeam but enough for overnight refill from empty.
Trade-off: the LR60R is the most expensive in the lineup and the proprietary charging cable is fragile. The replacement cable runs around 35 dollars, worth keeping a spare in the kit.
Olight Marauder 2, Best Variable Spot
The Marauder 2 uses a unique zoom-style head with a center thrower LED and a ring of seven flood LEDs. Run the thrower alone for a 1300-meter beam, the flood ring for wide work coverage, or both together for hybrid use. Total peak is 14000 lumens with about 3200 lumens sustained.
The magnetic charging dock makes refill painless, drop the light on the base and walk away. The proprietary battery pack is well-built with a fuel gauge and over-discharge protection. Pocket clip works for belt carry despite the 695-gram weight.
Trade-off: the magnetic charge connection is convenient but not waterproof during charging. The proprietary pack also means you cannot swap in fresh cells in the field, you must wait for a charge.
Nitecore TM10K Pro, Best Compact
The TM10K Pro proves that 4x21700 can still be reasonably compact. At 320 grams and 14cm long, it is closer in size to a 2-cell light than a 4-cell brick. Four 21700 cells in a 2S2P configuration feed a quad XHP35 HD array for 12000 peak lumens.
Sustained output is 2800 lumens, which is enough for most security or patrol work. The 480-meter throw is shorter than the dedicated throwers above, this is a flood-oriented design for area illumination. USB-C charging at 30W refills in about 3 hours.
Trade-off: the shorter body has less surface area for cooling, the light gets hot fast on turbo. The thermal step-down is aggressive, expect 45 to 60 seconds at peak before it drops to sustained.
How to choose
Output number versus sustained number
The peak lumen number sells lights, the sustained number tells you what you actually use. Always read the runtime chart and pick based on the output 3 minutes into a run, not the first-second flash.
Throw versus flood for your use
Spotting at distance needs throw, working at the truck or in the yard needs flood. Hybrid lights compromise on both, dedicated lights excel at one. Pick based on what you actually do at night.
Charging matters more than you think
A 4-cell light takes 4 to 8 hours to refill on a slow charger. Pick a model with USB-C PD at 30W or more if you use the light often, the time savings matter.
Cell access and replacement
Lights with user-swappable cells let you carry spares and continue work after a flat. Lights with proprietary packs are tidier but lock you into wait-for-charge use.
For related gear, see our guide on best 1 AAA flashlight for an everyday carry counterpart, and the best headlamp for camping for hands-free use. For details on how we evaluate flashlight output and runtime, see our methodology.
The 4x21700 class is built for users who need real sustained output, not a 30-second turbo flash. The X75 is the defensible pick for most buyers, the MS18 for pure throw, and the TM10K Pro for users who want the runtime without committing to a brick on their belt.
Frequently asked questions
Why four 21700 cells instead of two?+
A 4x21700 pack stores roughly twice the energy of a 2-cell light and can deliver higher sustained current without sagging the voltage. For lights pushing 5000 lumens or more, two cells run hot fast and step down within minutes. Four cells share the load, run cooler, and hold turbo output longer. The trade-off is weight and size, a 4-cell light typically weighs 600 to 900 grams compared to 250 to 400 grams for a 2-cell.
Are these flashlights legal to carry?+
In most US states, yes. A few municipalities restrict tactical flashlights with strike bezels or specific lumen counts, but the 4x21700 form factor itself is not regulated. Airline carry-on rules require the cells to be installed in the light or carried in protective cases, never loose in checked luggage. Check your local laws for any sustained-output limits before relying on a light for self-defense use.
How long does turbo mode actually last?+
Most 4x21700 lights advertise 15000 to 20000 lumens on turbo but step down within 60 to 180 seconds to protect the LEDs and driver. Real sustained output after step-down is typically 2500 to 4500 lumens, which is still bright enough for long-range use. Read the runtime chart, not the peak lumen number, when comparing models.
Can I use any 21700 cells in these lights?+
Use only high-drain protected or unprotected cells rated for the discharge current the light requires, usually 15A to 30A continuous. Samsung 30T, Molicel P42A, and Sony VTC6A are the common high-drain choices. Low-drain cells from laptop salvage or unbranded sources sag the voltage, trigger low-voltage cutoff early, and can overheat under turbo load.
What is the difference between throw and flood?+
Throw is the distance the light reaches before brightness drops below 0.25 lux, which is roughly full moon illumination. Flood is the spread of usable light close to the user. A thrower uses a large reflector or aspheric lens with a narrow hotspot, useful for spotting at 500 to 1500 yards. A flooder uses a small reflector or TIR optic for wide coverage at 50 to 200 yards. Most 4x21700 lights lean thrower, with hybrid options that balance both.
Morgan Davis
Morgan Davis writes for The Tested Hub.