The JET-II is a single CR123 powered light with a much larger head than other similarly sized lights. Up the front end of the head is a plastic bezel inlaid into the head which holds the lens in. The lens used in made of sapphire crystal as with all current JETBeam products. Below that is a relatively deep and wide textured metal reflector which is perfectly aligned with the LED emitter. Externally, the head has some nice looking aesthetic touches such as a raised lip towards the front and scallops machined around the middle area. The head actually comes in 2 parts, the neck is where the emitter and electronics are housed. It has a stainless steel ring which is another aesthetic touch, can be easily unscrewed allowing for the possibility of swapping with different reflectors or diffuser wands. Threads between the head and neck has a slightly sandy feel but fit very well together. Together, the head and neck are almost as long as the battery tube and tail cap combined.

The battery tube is very compact and is able to accommodate CR123 and protected 16340 cells with no problems. The bare aluminum surfaces of the battery tube is coated with an anti-oxidizing chemical. This is what gives the threads and inner walls the slight bronze hue. The threads are cut in the new style right-angle fashion which are thicker than regular threads and have sharp, rectangular edges instead of the regular smooth style. The threads are quite rough, after screwing and unscrewing the tail cap a few times for battery changes I noticed some powdery aluminum build-up between the threads. There are 2 rubber o-rings on either end of the battery tube fit very snugly and provides a good seal. Just like most other JETBeam lights, there are contact spring at both the "+" and "-" ends, this results in a very tight fit when inserting batteries. Externally, the battery tube has more than adequate knurling for grip. There are 3 flat faces and 3 long, narrow slots machined on it. The entire light is very consistently coated with Type 3 anodizing with no smudges or flaws to be found. The tail cap houses a reverse push button switch which provides a positive tactile feedback with average travel. The rubber cap is quite thick and provides additional tension, thought it also sticks out the end of the tail cap so the light will not be able to tail stand. The overall stiffness of the switch prevents the light from being accidentally activated when stored in pockets or bags. A band of knurling is machined around the tail cap for grip, and 2 narrow slots allow for lanyard attachments.

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

The JET-II I.B.S. uses a Q5 bin XR-E emitter which is advertised as providing maximum output of 225 lumens on CR123 or 16340 cells. Beam profile is narrow with a well focused, 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. Although the emitter and reflector seem perfectly aligned, the beam does have a black area to one side of the hotspot. My sample has a slight violet hue, cool color temperature.

The key feature to note in the JET-II I.B.S. is its infinitely variable brightness setting. In addition, it also has the strobe modes available as did the previous version of the JET-II. 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. The circuit does emit a high frequency sound at certain brightness levels.

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 16340 cells. For example, at 50% brightness on an CR123 cell, this is actually 50% in rough reference to the 100% level on 16340 cells. Not relative to the 100% brightness on an CR123 cell. Though because the 3.0V of CR123 and 3.7V of 16340 cells are quite close, the difference isn't as large as with the JET-1 MK.II. Although regulation is quite good, runtime seems a little short. As can be seen from the runtime graphs below. For some reason when running with a CR123 cell at 100%, the out drops within a few minutes and then consistently outputs at a much lower level. I would have attributed this to some kind of thermal protection, however this can't be the case since the 16340 manage to last longer at higher output.

[Update: 02 May, 2008] The JET-II I.B.S. gets pretty hot on 100% and the default high level with passive cooling (PC), hot enough to affect the performance of the lithium CR123 cells. So I've done another runtime with active cooling (AC) by having a fan blowing directly onto the flashlight during the tests. So what does this mean for the casual user? If you're using the light intermittently then you can take the the active cooled runtime as a guide. If you're using the light continuously at ambient room temperature, then take the passive cooled runtime.

The video below if from the MK.II review but is identical in showing the mode sequence on of the I.B.S. circuitry.

The Good - Convenient single handed operation for brightness and mode settings. Throws a very bright and well focused beam considering its size.

The Bad - Circuit is lacking in efficiency. Using CR123 cells is surprisingly bad at 100% brightness, but makes up for this by performing better at lower levels.

The Relative - Beam has a slightly cool color temperature. Uses a reverse push button switch. Emits a high frequency sound at certain brightness levels.

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).