the G2 i the basic entry level light
http://www.flashlightreviews.com/reviews/surefire_g2.htm
UPDATE: Surefire has affirmed that all current Surefire lights should be waterproof to about 33 feet/10 meters. Some reviews were posted before Surefire made the affirmation that their lights were watertight to 1 atmosphere depth. Any new Surefire lights you purchase now should be considered waterproof to 33 feet/10 meters.
UPDATE 2: The G2 now comes with a Lock Out Tail Cap! YESSSSS!!!! Something a lot of people have been waiting for. Now the least expensive Surefire has all the operational characteristics of their more expensive lights. Be careful, though, there are a lot of older G2's on the market still to cycle through before you can be sure that every G2 has the LOTC. I bought one of the new LOTC G2 lights and it's great! No more accidental activations in your pack or bellybag.
Short Description:
The G2 is made by Surefire as a (relatively) low cost alternative to their other personal lighting products. It has all the features of the standard 6P, but is made of a special plastic called "Nitrolon", making it lightweight and very impact resistant. The unit reviewed is labeled as a "CandlePowerForums CPF 50 Special", but other than the label on the bezel, it is identical to production run G2 lights.
The G2 is available in black, yellow, or olive-drab. As mentioned, the body of the light is made of Nitrolon, a very tough plastic compound exclusive to Surefire. The body tube has a waffle pattern molded into it for grip. Inside the body tube is a metal sleeve for conducting electricity and completing the circuit when in use. The bezel has ridges around its base, again for grip, and also to serve as an anti-roll device. The tailcap likewise has ridges and the rubber pushbutton switch is checkered for grip. The light is sealed throughout with o-ring seals.
The G2 accepts the standard P60 Surefire lamp assembly for 60 minutes of runtime at 60 lumens on a set of batteries. You can replace this with the P61 Surefire high output lamp assembly for a runtime of 20 minutes at 120 lumens. The reflector is integral in the lamp assembly and is textured to smooth out the beam of light.
The switch is a combination switch on the tail of the light. Push the button for momentary on-off or twist the entire tailcap for constant-on. (See "UPDATE 2" at top of page)
The G2 uses 2 123a lithium batteries for power. These provide a total of 6 volts with a runtime of 1 hour with the standard lamp assembly. Batteries are included.
The light has O-rings on the head and bezel and inside the tailcap switch assembly and is only considered "water resistant".
A wide variety of accessories are available for the light from Surefire.