I use these on my job in a theater. The red beam is preferred when I have to go into an auditorium where a show is running to look for something or handle an issue; a regular flashlight with a white beam would be extremely distracting in such a situation. The red beam preserves vision and doesn't leave you seeing spots after the light is off the way a white beam would.
The construction is good. Nothing feels too tight or loose. I was concerned that the adjustable head would be too loose, but it seems to keep its position well enough considering it's frequently being inserted into and removed from a pants pocket. It's even stood up to a couple of minor drops from about 4'. I haven't had a chance to try them with 18650 batteries, so I can't comment on that yet. There are two plastic sleeves included with the lights, which I assume are adaptors for the 18650's...you probably don't want to lose those, but if you do, the lights still work well on 3 AAA's.
The only thing I'm not happy about is the lack of a momentary on function as part of the switch. I won't dock a star for that since I didn't notice that before ordering, an oversight on *my* part.
Overall, I'm quite satisfied with the lights.
About AuKvi AuKvi, focuses on creating the best lighting experience. Only high end LED and advanced optical design are adopted. Enjoy lighting with AuKvi Flashlight Features: 1) Brand:Aukvi 2) Manufacturer:AuKvi 3) Wattage:10 watts 4) Material:Aluminum Alloy5) Max output :500 lumens 6) 5 Mode: High / Medium/ Low / Strobe/ SOS 7) Lighting Distance:150-200M 8) Focal Length:Adjustable 9) Size(mm):144 x 38(bezel)/22(body) 10) Net Weight (g): 130g 11) Color: Black. Power Source： 1 x 18650 Battery(Not Included) OR 3 x AAA(Not Included) Package: 1 x AuKvi Flashlight (Battery Not Included) How do you change the modes on this flashlight? The toggle option occurs if the button is not fully depressed prior to releasing it. The option that was last used when the light was shut off is the option you will start with when turned back on, unless the light is turned on and off in a rapid manner. Seller Warranty: 6 Month Replacement Warranty Warning - 6 mth Warranty Only Valid if Purchased from Aukvi (Seller)