Highlights Helpful for checking for bubbles underneath a lens Pocket clip activates light (must sustain pocket clip pushed down to keep light on) Works with DMV Luma-Serter Plus for light-guided insertion 5" x 1/2" Rebecca's description Who is Rebecca? I added these to the shop because we've heard from many scleral lens users who find them handy for checking for bubbles. They're manufactured and sold for eye doctors, so they have a pupil gauge, but they're a practical tool for some of us as well. UPDATE (October 2021): We are now stocking the DMV Luma-Serter Plus, which fits perfectly over the end of this penlight for light-guided insertion. I find it somewhat annoying that they call them disposable. I supposed it's a euphemism for "cheap, so don't expect it to last for years", but it's not like they are single use. Manufacturer's description They'll Keep On Working, You Won't Believe They're Disposable These penlights will keep working for months or even years, you'll find it hard to believe that they're disposable. The high quality molded plastic body also gives these penlights that premium penlight feel. More For Less Primacare Disposable Diagnostic Penlights are simply the most affordable high quality disposable penlights out there. These penlight pack will make sure that you always have a penlight handy, anywhere in the office or everywhere you go. Helps You Get Accurate Readings A very handy pupil size chart/guage printed directly on the penlight body will help you easily measure your patients pupil size as you examine their eyes. The measurement chart ranges from 3 to 4 millimeters. Features Disposable penlight with sealed concentric beam and pinpoint lens to illuminate the eyes, ears, and throat Dual-function pocket clip for portability and for activating the pen light Pupil gauge printed on the body of the penlight for determining pupil size LED penlight Measures 5" in length and 1/2" in diameter