On any given day in the ED, I use my super-bright penlight 2-5 times a day. It is amazing what things I’ve almost missed without a bright LED flashlight.

  • Subtle HSV-2 labial ulcerations in a female patient with dysuria
  • Additional scalp lacerations hidden in the hair
  • Tonsillar exudates in a patient with strep pharyngitis
  • Unequal pupillary responses in a brightly lit trauma room in a head-injured patient

I wanted to revisit a prior post about the importance of changing your Tungsten penlight to a LED light.

There apparently is a whole world of LED enthusiasts, debating and talking about the latest and greatest in LED technology. There is constant competition amongst companies to generate the most efficient and brightest lighting.

Although I have no clue about this topic, it’s nice to have techie friends who do! It’s how I found out about the company 4Sevens and the Preon flashlight. (I do not have any financial affiliations with 4Sevens, besides the fact that they have my $49 for purchasing the penlight.)

LED Flashlight

The XP-G LED light, developed by the company Cree, can emit a super bright light with minimal power requirement. The company 4Sevens has developed the first AAA-battery powered Cree XP-G LED penlight, called the Preon flashlight. Most kits, which vary based on the outer shell color, are currently on back-order because of the recent release and great press about the flashlight kit.


I just got my red Preon kit in the mail and the light is indeed “absurdly bright”, as the website touts. It fits nicely in my scrub top pocket because it really is the size and shape of a pen. Also, it takes commonly available AAA batteries, which I have in rechargeable form.

When you order it, it comes in a set. You can assemble a short 1-AAA battery penlight, or attach a longer barrel to build a brighter 2-AAA battery penlight. There are 3 settings – low, medium, and “ack! I’m blinded” high just by lightly tapping on the clicker.

Check out how much light this little penlight emits in a dimly lit room!

So, I retired my recent LED light, which was the size of a roll of quarters and could fit easily in your palm. I’ve always loved its bright output. The problem was that I didn’t have a great way to carry it. It was too bulky for my scrub top pocket. And when I kept it in my scrub pants back-pocket, I would often accidentally sit on it and turn it on. My butt would be aglow for hours before anyone told me! A waste of a pricey lithium battery.

What did I do with my old penlight? I passed it along to an uber-enthusiastic EM resident who was always admiring the penlight whenever I used it. When I gave it to him, he was so over-the-top excited that I felt like I was passing him the Olympic torch or something.

Michelle Lin, MD
ALiEM Founder and CEO
Professor and Digital Innovation Lab Director
Department of Emergency Medicine
University of California, San Francisco
Michelle Lin, MD


Professor of Emerg Med at UCSF-Zuckerberg SF General. ALiEM Founder @aliemteam #PostitPearls at https://t.co/50EapJORCa Bio: https://t.co/7v7cgJqNEn
Michelle Lin, MD