• You must be a Supporting Member to participate in the Candle Power Forums Marketplace.

    You can become a Supporting Member.


Not open for further replies.


Nov 26, 2002
Old World

What is it?

The McLuxIII-27LT is another light of the McLuxIII-Series. Just like the McLuxIII-PD and its brethren as well as the HD45 it is a fully regulated 2-stage light making use of dat2zip's x2-Converter Series.
The 27LT is a stand-alone light and isn't compatible with any other McGizmo offering to date. It is a rather obvious merging of the PD with the HD45 in terms of size, performance and function. It is heavy, beefy in wall thicknesses and should be capable of survival in demanding and unfriendly conditions.



The 27LT is made of aircraft-grade aluminium and sports a significant wall-thickness making it quite tough and ready for some abuse. It is hard-anodised in dark-slate-grey, almost black, just like most of the recent McGizmo regular offerings.
Its reflector is the McR-27L, an elongated version of the famous McR-20 used in the McLuxIII-PD and Aleph2 line. The LED and reflector are protected by an optically coated 2mm thick sapphire window. A bezel-down bead-blasted titanium clip is attached to the tail of the light, and there you also find three holes for lanyard attachment. The tail is flat and the light can thus be used in candle-mode if you like.


The light is completely anodised inside and out as the electrical path is made via a nickel-plated brass piston that rides in the battery tube. Negative contact is made by a silver plated spring soldered to ths piston.


As can be seen in the pic above there is a double o-ring seal present.
The driver is a DBx2 by Wayne Yamaguchi, and it works just like with the HD45 and PD lights ... meaning low mode is established via the well known kilroy and high mode kicks in when the brass contact ring touches the piston, too. For a detailed analysis of how the driver works please have a look at the McLuxIII-PD FAQ.

The 27LT uses a Joker-UX1K paired with a Joker-version of the 27LT reflector for optimum focus and maximum lux/throw.

How does it work?

Very easy. Just twist the head to achieve low-mode and twist further for high-mode. No momentary modes are available with this light.

The driver, LED and batteries

The DBx2 (DownBoy) is a current regulated buck driver which means you can use any battery configuration from the Vin of your LED up to 14V input voltage. Considering the physical limitations of the light this leaves the following battery combos as realistic alternatives:
- 2xCR123
- 2xLi-Ion (R123)
- 1xLi-Ion --> only the slim PILA 168S will fit, the 168A is too fat.
On 1xLi-Ion it depends on the Vin of your LED wether the driver will be in regulation or not. If the batteries can no longer provide enough power to maintain current regulation, the light drops in direct-drive mode and gradually dims down. No damage will occur to the light if you suck your cells dry, but unprotected Li-Ion cells might suffer a premature death from this.

Note :caution: : I only know that my PILA168S fits in this light, and I have no experience with other Li-Ion cells or the new PILA cells.

Note :caution: : There might be an issue with 2 x R123 and the DBx2 driver. For more info see this thread:

The regular run of 27LT lights sports a LuxeonIII LED with the bin UX1K.

How big is it?

The light isn't that big, but relatively heavy due to the wall thickness and piston. Some pics for size comparison:

SF U2 and 27LT

McLuxIII-Series: HD45 / 27LT / PD

What's coming out of the business end?

Light. Light collimated by the McR-27L, which is light collimated in a very efficient manner into a perfectly balanced and useful beam.
The McR-27L produces a very tight and bright corona with a gently fading bright hotspot. This makes the illuminated area much bigger AND as the corona has significant strength and reach, the light is much more useful at medium distances as some other variations, especially the widely used McR-27 lights. And it is easier on the eyes due to reduced contrast between hotspot and corona.
You get one of the most perfect and useful beams with this light.

Here is a beamshot comparison between the 27LT and the Aleph line. While the camera settings and surrounding conditions are a fixed environment, there is the Luxeon Lottery and bin difference between the 27LT and the Aleph LE used. The Aleph shots however are fully comparable.
You'll see a standard white-wall shot and an underexposed white-wall shot for hotspot comparison as well as a comparison collage including a room-shot:



Comparison pic:


Output data

To be taken with a grain of salt and the usual :caution: words of caution.

The drive levels are 100mA for low and 917mA for high, both constant current regulated.

Don had two units of this run tested in an independent lab and they got both 68 lumens out the front end.
My unti measures 3640 lux. With my lightmeter.

Here's a runtime graph for low and high mode:


Attachment options

There is the well-known ti-clip as well as the above-mentioned three lanyard-holes in the tail.

Will there be other versions?

Currently there are no plans to release other versions of this light except of maybe a small number of LuxV units. Please do not send custom requests or questions about alternate configurations as there won't be any on demand. Sorry.
This "no" includes tritium slots.

How rugged is it ... and what about deep-sea expeditions?

The 27LT should be a very tough companion and will withstand a lot of abuse. If properly maintained (o-rings lubed and dirt removed) it will work underwater. Don has used those lights underwater excessively without any problems. The light ships with Krytox 50/50 lube which is available at the Sandwich Shoppe.
Don sais: "It is not a dive light but with proper care to seals, this light should handle pressure better than its user."

Is it moddable?

No and yes.
The 27LT has an integral bulkhead like the PD and the LED is arctic silver epoxy bonded to this bulkhead. The DBx2 converter can be easily removed by taking out its retaining screw and then unsoldering the two LED lead wires. At that point, you can heat up the head to 175F or hotter if you want and you can destructively remove the LED.
At that point, you could install a 5W LED if you wanted and probably get a BBx2 driver from Wayne if your reason was to go to a 5W system. There will be a null or donut in the beam with a 5W LED. The milled pocket in these heads will not accomodate a K2 LED. Modifications to host a K2 would be easy and straight forward for anyone with the proper equipment.

New LEDs and drivers

A limited number of LuxV and NBBx2 equipped units have been made and sold mostly via the Shoppe.

In the advent of the new generation power LEDs the 27LT will be equipped with the Seoul P4 LED that offers very similar beam characteristics as the Luxeon LED with more power and less heat. The light is then called the McLuxIII-27ST.

In the end, the 27LT is a simple and tough light, and it has one of the best beams available with a KISS (keep it super simple) interface, meaning two regulated levels of light. Nothing more, nothing less.

McGizmo Marketing Department :D
Last edited:
Not open for further replies.