Review: Malkoff M91B LED Drop-In


The M91B is the newest addition to the Malkoff Devices line of LED drop-in modules. Like its predecessor, the M91A, the new M91B is designed for use with the Malkoff line of full-size flashlight bodies or as a direct drop-in replacement for the SureFire P90 incandescent lamp assembly used by the SureFire 9P, C3 Centurion, and Z3 CombatLight.

Suitable for handheld and weapon mounted applications, the new M91B is outfitted with a cool white Cree XP-L emitter rated to produce approximately 825 lumens at turn on and 700 lumens during continuous operation. When used in conjunction with a Malkoff flashlight body and high/low bezel ring a 30 to 40 lumen (approximately) low mode is also available. The M91B has a retail price of $89.00.

Malkoff M91B – Overview

At first glance the new M91B looks like any other Malkoff drop-in with its distinctive design and solid brass heatsink. However a look inside the custom orange peel reflector reveals the Cree XP-L emitter, a first for Malkoff Devices.

Malkoff M91B LED Drop-in for SureFire 9P, C3 and Z3

The brass heatsink is sized to fit perfectly in Malkoff or SureFire hosts without the use of an outer spring. A small center spring is used to maintain electrical contact with the battery and all electronics are fully potted for durability.

Malkoff M91B LED Drop-in for SureFire 9P, C3 and Z3

When installed in a Malkoff bezel the M91B may be used with the MD2, MD3 or MD4 flashlight bodies permitting a wide variety of battery configurations.

Malkoff M91B LED Drop-in for SureFire 9P, C2 and Z3

Installation in a SureFire host is as simple as removing the bezel and replacing the stock lamp assembly with the M91B.

Malkoff M91B LED Drop-in for SureFire 9P, C2 and Z3

Malkoff M91B – Performance

The large XP-L emitter and relatively small reflector produce what could be characterized as a floody beam that still has good reach. The broad center hotspot has a slightly off-white tint and is surrounded by a very large corona which tapers off into the remainder of the spill beam. The outermost portion of the spill is noticeably cool but the corona has a slight yellow tint which gives the overall beam a warmer appearance. There are some rings present in the beam but they are most obvious when illuminating nearby objects (white wall hunting) and were not an issue in normal use.

Malkoff M91B LED Drop-in for SureFire 9P, C2 and Z3

When compared to the previous M91A, the M91B provides a boost in both total output and beam reach, with its broad hotspot providing good illumination out to 60-80 yards. The following slides compare the Malkoff M91B to a variety of other lights to provide perspective with regard to output, beam profile, and beam tint. The beamshots can be compared across the full width of the image using the slider and additional comparisons may be accessed using the navigation buttons in the bottom-right corner of each image.

The following lights are shown for comparison:

  1. Malkoff MD2 with M61 drop-in (Review)
  2. SureFire P2X Fury (Review)
  3. Elzetta Bravo AVS (Review)
  4. Malkoff MD2 with M91 drop-in
  5. Malkoff MD3 with M91A drop-in
  6. FourSevens Maelstrom Regen MMR-X (Review)
  7. Elzetta Charlie AVS (Review)
  8. Malkoff Hound Dog V3 (Review)
  9. Malkoff Wildcat V4 (Review)
  10. Malkoff Wildcat V5 (Review)

Beamshots – 30 Yards to Swing

Beamshots – 40 Yards to Swing


With its wide operating voltage range, the M91B can be powered by two lithium-ion rechargeable batteries or from 2 to 4 CR123 lithium primary batteries. Malkoff MD2, MD3 and MD4 bodies were used to conduct runtime testing with several of the most frequently used battery types.

The CR123 lithium primary batteries used in these tests were provided by Battery Station.  Their support has been invaluable.

Malkoff M91B LED Drop-in for SureFire 9P, C2 and Z3

Due to the large number of tests, the results are separated into two charts, one for rechargeable lithium-ion batteries and other for CR123 lithium primary batteries.

Malkoff M91B Runtime with rechargeable batteries

The output level was extremely consistent between the various types of rechargeable batteries used during the test and all battery types maintained very stable regulation. Protected batteries (AW 18650 3400mAh, AW 18500 1500mAh, and AW 16340 750mAh) all ran until their overdischarge protection circuit was activated causing the light to shut off completely. During tests with the IMR batteries, the light began to blink on and off when the operating voltage dropped too low.

Malkoff M91B Runtime with CR123 batteries

Output and regulation were also very stable when the M91B was powered by either 3 or 4 CR123 cells (2 x AW 18650 3400mAh from previous chart shown as a baseline). The drop-in is not intended for use with only two CR123 batteries but testing verifies that this would be possible in an emergency, although output and runtime would be less than the other configurations.

When operated continuously, the light became very warm but not quite too hot to hold.

Malkoff M91B – Conclusions

The Malkoff M91B is a very powerful drop-in and is also extremely versatile due to its broad support for a number of different battery options. It is well suited for use in hosts such as a stock SureFire 9P although larger hosts that can accommodate 18mm batteries, such as the Malkoff MD4 body, are necessary to achieve maximum performance. Output is consistent across the different battery configurations and regulation is rock solid. Construction is top notch and I can’t think of any type of usage that would be more than the drop-in couldn’t handle.

Malkoff M91B LED Drop-in for SureFire 9P, C2 and Z3

I consider the beam produced by the M91B to be more useful than its predecessor, the M91A.  It’s not so much a matter of sheer output but rather the slight increase in throw makes a noticeable difference when used outdoors.  Also, in contrast to the very cool white of my M91A the warmer tone of the M91B is easier on the eyes.  Those in search of the “perfect beam” likely won’t be satisfied by the coloration and rings present in the M91B but these have proven to be non-issues in my use so far.

As always when purchasing from Malkoff Devices, the order was shipped promptly, arrived safely, and included a handwritten note of appreciation.  This is one company that is always a pleasure to do business with.

Visit the Malkoff Devices website for more information about the M91B drop-in.

Posted in Flashlight Accessories, Flashlight Reviews, Malkoff Reviews and tagged , , , .


  1. Thank you for the review Jim, I was afraid that the tint either too bluish, but that is not the case on the beamshots.

    I will mount the M91B in my MD3. 🙂

  2. Hi Jim, what is the runtimes in low mode please? And is it technically somehow possible to include an medium mode within that flashlight?


    • Hi Thomas. I’m afraid I haven’t tested the low mode runtime with any of the Malkoff drop-ins. I’m certain that it would run for many hours (depending upon the batteries used) and I’m not set up very well for really long runtime tests.

  3. Hi Jim, thank you for your reply.

    Could you please add photos for low mode to your review?

    This would help to identify how usefull it is, since even runtime with 2x 18650mA Li-Ion rechargeables is highly limited.


  4. Awesome review, thank you! Can I ask what software you use for the beamshot comparisons, and if it’s available stand-alone (i.e. not published to web)? I’d love to be able to take my personal lights and compare beamshots split-screen like that. Sometimes with separate pictures, it’s difficult to compare spill size, intensity, etc. Awesome idea, thank you!

    • Hi Mike. The beam comparisons are created using javascript (I think that’s right) which renders one image on top of the other on the web page. The slider then reveals the picture on the bottom when you slide it to the left (I hope that makes sense). Off the top of my head I can’t think of a way to do it in a standalone fashion.

Share your thoughts!

This site uses Akismet to reduce spam. Learn how your comment data is processed.