I gotta couple of TACMIII lights as well as some SUREFIRE and INSIGHT units. They all work well. Sure, the TACM's are NOT sexy, they are made of some pretty darn durable plastic, and they don't have the "high speed/low drag" factor, but they work, throw the same lumen values as SF 6 volters with the P60 bulb, and don't cost a fortune.
Biggest negatives are the switches. I hate tape/membrane switches, they are fragile and I hate having cables and wires hanging from my rifle to snag on stuff. Both my units, which are older TACM units, have a twist cap on the back to activate. You can push on the cap to get a momentary beam, but you have to push hard and keep the pressure on to keep the beam on. The current units have a real nice momentary push button on the back cap. I might have to upgrade mine.
Go ahead and buy the TACM lights. They are damn bright and just about indestructable. They just don't have the "hey I have the same rig that Seal Team 6 uses" factor
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Hope this helps.