TL;DR. Aluminum body with o-rings. Single switch off/low/high. 50M is garbage, 250M is great for a AAA light. All of the 300+ series use AA batteries and are extremely bright with a useable low mode.Longer version: I am late Gen-X. I have had thousands of flashlights in my life, from the old lantern battery incandescent to very expensive rechargeable tactical LED models of recent years. I was a farmer, a military man for 20 years, search & rescue, mortuary affairs, Army Corps of Engineers, USFS ... I used lights. A lot.After all of that, I really wanted a simple, robust, quality flashlight. Luckily, I finally found it. Unfortunately, most of the models in this range have been discontinued. Once I found that out, I bought a dozen for myself and some for friends and family before I left this review. I will buy more.I wear a men's large glove. The 300M, 325M, 350M, and 425M all have a larger circumference for the 3 or 6 AA batteries and fit comfortably in my hand. They will likely feel bulky for anyone with small hands. For that, the 250M is a 3 AAA light and much more compact. The 50M is garbage.The first photo shows the models in the range I was able to get. From left to right are the 50M (1AAA), 250M (3AAA), 300M (3AA), 325M (3AA), 350M (6AA), and 425M (6AA). The 50M is regrettably dim and not good for much more than checking charts on the night rounds. There are better lights for that. The 250M is quite bright. For anyone looking for an inexpensive flashlight and isn't worried about needing more than an hour of runtime, it's pretty good.The 300M and 325M appear to share the same body. The 300M is rated at 350 lumens with a three hour runtime on high and the 325M is rated at 500 lumens with a two hour runtime. The 350M and 425M appear to share the same body, but the 425 is 27 grams heavier with a longer lens. The 350M is rated at 750 lumens for three hours on high and the 425M is rated at 625 lumens for three hours on high.I really liked the 350M, so I tested it against a Maglite 2D LED at six feet. The picture shows the Coleman 350M on the left and the Maglite on the right. The Maglite is now stored with our emergency lanterns. Then I tested the 350M with the included alkaline batteries against a 350M using Panasonic Eneloop rechargeable batteries. The 350M using rechargeable batteries was brighter, but it only lasted about 85 minutes before dimming considerably.I dropped all of them from six feet and saw no damage. All continued to function perfectly. The aluminum construction with O-rings and the plastic grip shield seem sturdy (IPX4 rated). I didn't crack any lenses by dropping them. They compare well to more expensive flashlights I've owned, but have a more traditional construction with a grippy sleeve on the lens end instead of a smashy tactical bezel. The wider lens structure would make them unwieldy for belt carry, but exceptional for anything around the farm or home.Small sized:50M: 1 AAA battery. 75 lumens for 3 hours or 2 for 200. Garbage.250M: 3 AAA batteries. 325 lumens for 1 hour or 4 for 200. Useful on high.Medium sized:300M: 3 AA batteries. 350 lumens for 3 hours or 10 for 200.325M: 3 AA batteries. 500 lumens for 2 hours or 10 for 200. (discontinued)Large sized:350M: 6 AA batteries. 750 lumens for 2 hours or 20 for 200. (discontinued)425M: 6 AA batteries. 625 lumens for 3 hours or 20 for 200. (discontinued)The extra long sizes have been discontinued and I can't find any NIB, so I left them off. If you're a grumpy gen-xer or older, like me, you'll probably like these. If you found this helpful, please rate my review. I like reviewing things and it helps me to know if they're helpful.