The Mark II is the next version of, and replaces, the original JET-I. Since the Mark II has so much in common with the original version, I am not going to repeat the entire review here. Instead, I invite you to please read the JET-I Review, and then apply the updates listed below. Consider this to be "chapter two" in the JetBeam JET-I story...

Quick Recap: The JETBeam JET-I Mark II uses a single 3 Watt Luxeon sitting behind a sapphire crystal lens with an internal AR coating. The aluminum reflector has been custom designed to help with the tint of the light produced by the LED, resulting in a very white light output. It uses a special boost circuit that helps regulate light levels and has three levels of output plus a strobe mode. Normally running on a single AA (alkaline, lithium, or NiMH) you can purchase a 123A tube or an extension to run the light on 2 AA cells. Even AAA cells can be used if that is all that is available. The body is Type III anodized aluminum for light weight and durability. Dual O-rings seal both ends of the light for a high degree of water resistance. The tailcap switch covers are interchangeable and the tailcap has notches/holes for attachment of a lanyard.

Updates: The JETBeam JET-I Mark-II is essentially the same as the original JET-I with with the following updates:

Body:

• Glow In The Dark (GITD) tailcap switch cover (looks yellow in normal light).
• GITD ring at end of reflector behind lens.
• No more glow paint in grooves on sides of AA case (empty grooves).
• Two orange O-rings on both ends of the 1AA battery tube, same on both ends.
• The flat side panels are a little smaller.
• The square checkering around the tailcap has been replaced with diamond checkering.
• The laser etching looks more refined.
• MkII etched on the side of the head opposite the serial number.

Switch:

• 3 levels of output now, plus strobe.
• Click on for "normal" output (65% of max, PWM).
• Click off, then click back on within 2 seconds to change modes.
• OR soft-press switch anytime while on to change modes.
• 2 second or greater pause after clicking off resets the sequence.
• Mode sequence: Normal, Low, Max, Strobe, Off.
• Strobe is VERY annoying - like Gladius/StrikerVG strobe.
• The mode change soft-press can be very quick. After clicking on I can get it into the strobe in less than 1/2 second (really!).

Other:

• Different belt sheath. Looks more like the Fenix now instead of the original with flap. I prefer the original, but with the flap the tailcap GITD is covered up.
• No need to clean up the battery tube ends with sandpaper for better contact. This issue has been resolved.
• The 123A tube from the original JET-I fits, but, it just barely screws on enough to cover the highest point on the O-ring. Looks like you may need a new 123A tube to fit the new head if you have an older tube. I'll bet it's because the electronics in the head moved the contact plate back on the threads a bit.
• The 2-AA extension tube fits fine.
  

New vs. Old - side-by-side

A quick note about the GITD ring in the bezel and the tailcap cover. The glow is subtle. In the dark - the real dark - you'll be able to very quickly pick out the light. If there is background light, you may not see the glow well, but then again, you can probably see the JET-I without needing the glow either.

Output: From the original review, you already know what the circuitry inside the JET-I can do. Now we have 4 output options: Normal (65%), Low (5%), Max (100%), and Strobe. The strobe is very annoying, like the Gladius or StrikerVG strobes which are designed for tactical use.

Dimming is accomplished using PWM or Pulse Width Modulation. The LED is flickered very rapidly to give the illusion of dimming. Your eyes do not perceive the flicker unless you move the light quickly across a surface or if the subject being illuminated moves quickly. The flicker may be perceivable when reading in the dark using the light, and some folks find this annoying.

I did note (and you probably will, too) that the Max output is less than the original JET-I. The maximum output produced by one AA alkaline has dropped by about 18%. The rest of the output numbers have dropped as well.

Runtime Plots: More runtimes will be added as time allows. So far, I'm seeing a drop in the runtimes relative to the original model. I wonder if the new circuit is drawing a fairly significant amount of power, or if something else is going on.

1 AA alkaline cell, tested at the "Normal" (65%) setting.

Runtime completed with Rayovac brand batteries. More information on runtime plots is available HERE.

1 AA alkaline cell, tested at the "Max" (100%) setting.

Runtime completed with Rayovac brand batteries. More information on runtime plots is available HERE.

1 AA alkaline cell, tested at the "Low" (5%) setting.

Runtime completed with Rayovac brand batteries. More information on runtime plots is available HERE.

1 AA Lithium cell, tested at the "Max" (100%) setting.

Runtime completed with Energizer L91 brand batteries. More information on runtime plots is available HERE.

Photo Gallery:

In package, and new sheath

Tailcap, glow close-up

Glow ring in bezel, above reflector

Side grooves empty of glow material

What I Liked: Water resistant, Tough HA-III finish, Impact resistant, Regulated, Good battery life, Bright, Easy battery change, Lightweight, Lots of battery options, Multiple output modes

What I Didn't Like: Nothing.

Picky Little Things: A little bit of a drop in output and runtime relative to the original version, but not horribly so. Quite possibly a give-and-take for having the new multifunction circuit added in to the system.

Conclusions: We all have our "flavor of the month" when it comes to our favorite things. I suspect that this latest version of the Jet-I is going to be quite a bit more than that. The folks at JetBeam first created a light which had excellent features and capabilities and have now improved upon it without adding a ton of useless garbage, as is what often happens when something is "improved" by its maker.

The new switching is quite well done and the output options are super. The 65% "Normal" mode preserves battery life while giving plenty of light. The 5% "Low" mode is great for night time use.

Adding the GITD tailcap and glow ring in the bezel just makes sense. I don't know about you, but a light on my nightstand has the tailcap pointing up, toward the bedside light, where a GITD tailcap switch can get a good charge before turning the light off for the night. Likewise, the glow ring in the bezel charges when the light is turned on, unlike the side panel glow paint in the original JET-I.

Quick Facts Table: