The JET-1 MK.II I.B.S. is identical to the earlier MK.II R aside from the I.B.S. branding on the head. The MK.II I.B.S. has a very clean designed head, the coating on the exterior of the head is nice, smooth and consistent. The coating is a gray with a slightly brown hue. Aside from the branding printed on the bottom area of the head’s exterior, there aren’t any other aesthetic touches on the head. The MK.II I.B.S. is advertised as using a sapphire crystal lens, as with all JETBeam products. An orange rubber o-ring sits between the lens and reflector which provides a good seal as long as the emitter module is screwed in securely. The reflector and emitter are very well-aligned with each other, the reflector is slightly deeper than other lights of similar. The emitter module isn’t adhered or permanently attached to the head in any way so you are able to easily unscrew it from the rear of the head. The “+” contact has a gold coated spring soldered to the PCB which means that flat topped 14500 cells can be used without problems. Threads on the head are of medium thickness, not too fine and well-machined. They don’t cause any grinding or squeaking when being screwed onto the battery tube.

The battery tube has the same consistent and well-finish coating as the head. Color of the coating is also well matched with that of the head. There are 3 flat faces, and 3 horizontal slots machined along the length of the battery tube. The flat faces give adequate grip and the horizontal slots are deep enough to small tritium vials in if you want. The walls of the battery tube are quite thick, so it shouldn’t be easily dented or damaged. Protected 14500 cells will fit without problems. Threads on either end of the battery tube are well-machined as well, medium thickness and well-cut. I did not experience any grinding or squeaking while screwing on the head of tail cap. There are also 2 orange rubber o-ring on either end of the battery tube, just before the threads. I find them slightly too thick though, screwing on the tail cap you’ll experience that it’s noticeably more resistance than other lights such as the Fenix lights. Then again, a good thing about this is that the seal provided by these o-rings are that much more secure. There’s a band of knurling about 0.8cm wide around the tail cap which provides good grip when unscrewing during battery changes. You can attach lanyard attachments to either of the 2 rectangular slots machined at the end of the tail cap. The MK.II I.B.S. comes with a bright yellow push button cap pre-installed which can be changed to the slightly more subdued orange one also included in the package. Inside the tail cap is a regular reverse push button switch, so momentary activation isn't possible. The switching mechanism has short travel and tension is above average, while not being too hard to press. The push button switch cap is recessed within the tail cap and allow the MK.II I.B.S. to tail stand on flat surfaces easily. One thing to take note about screwing on the tail cap after inserting a battery in the MK.II I.B.S. is that they can be quite a tight fit due to the springs on both the “+” and “-“ contacts.

If you're unfamiliar with any of the terms used in this review, click here for explanations on common flashlight related vocabulary.

The MK.II I.B.S. uses a Q5 bin XR-E emitter which is advertised as providing maximum output of 130 and 225 lumens on AA and 14500 cells respectively. Beam profile is well focused which has a well defined hotspot area and spill beam. It looks cleaner than the beam profile produced by the Fenix L1D CE with textured reflector which has a corona around the hotspot. Of course this is relative to each user depending on what kind of beam profile they prefer. My sample has a slight violet hue, cool color temperature.

Obviously the most important feature to note in the MK.II I.B.S. is its infinitely variable brightness setting. In addition, it also has the strobe modes available as did the MK.II R. Any of the brightness levels and strobe modes can be programmed into 3 "slots" if you will. Referred to as Mode A, B and C and are arranged in the following order.

Off > Mode A > Mode B > Mode C

There is no memory feature as far as mode sequence is concerned, thus the light will always start on Mode A when first turned on.

Activating brightness ramping.
Simply half-press the switch 3 times within 1 second. The ramping always starts from 5% brightness, up to 100% brightness. As a reminder, the light blinks twice at 5% brightness, twice again at 50% brightness, and thrice at 100% brightness. When the 100% brightness level is reached, it cycles back from 5% brightness. Switch off the light for at least 2 seconds at the desired brightness levels and it will be set. No effects of PWM was noticeable even at the lowest 5% brightness level.

Activating strobe modes selection.
While in the brightness ramping mode, half-press the switch once. The light will cycle through all the available strobe modes in the following order. As with the brightness ramping, the sequence is cyclical. Switch off the light for at least 2 seconds at the desired strobe mode. Switch off the light for at least 2 seconds at the desired brightness levels and it will be set.

Ramps from 1Hz to 15Hz > Beacon > Double Blink > 100% S.O.S. > 5% S.O.S.

Reset settings.
While in the Strobe selection mode, half-pressing the switch once. The light will turn off although the switch is clicked on. Now, turn off the light for at least 2 seconds. The next time the light is turned on, Modes A, B and C will be set as factory defaults.

The way the electronics control the brightness setting seems suited for running on 3.7V 14500 cells. For example, at 50% brightness on an AA cell, this is actually 50% in rough reference to the 100% level on 14500 cells. Not relative to the 100% brightness on an AA cell. Although regulation is quite good, runtime seems a little short. As can be seen from the runtime graphs below. This seems to inherit the problem from the JET-1 Pro where runtime is shorter while at a lower brightness level when running on an AA cells.

The Good - Convenient single handed operation for brightness and mode settings. Clean beam profile which is noticeably brighter than the MK.II R.

The Bad - Circuit is lacking in efficiency as the JET-1 Pro did which results in shorter runtime on a lower brightness level when running on an AA cell.

The Relative - Beam has a slightly cool color temperature. Uses a reverse push button switch. No longer emits a high frequency sound on lower levels as the MK.II R did.

Head (front view).

Head (side view).

Head (rear view).

Battery tube (front view).

Battery tube (side view).

Battery tube (rear view).

Tail cap (front view).

Tail cap (side view).

Tail cap (rear view).