mW=milliwatt (1000 of a watt)
nm=nanometer (a measure of wavelength)
650nm=red/532nm=green/405nm=blu-ray
and a lot of others.
These are the ones you will most often come across in laser pointers.(other nm's are big $$$$)
405nm burns the best but is expensive. Around $1-$1.50 a mW.
Red is the cheapest way to go for burning power. Around .25 cent mW.
To pop balloons you need at least 50mW of red or green or 25mW of Blu-ray.
To light matches you need at least 200mW of red or 50-75mW of Blu-ray.
I don't recommend 532nm, (green) for burning, to a beginner, because of the danger of the brightness and the IR (infrared) leakage. (you must buy goggles to use inside, with all nm's)
But it falls in the middle between 650nm and 405nm
However, if you want the most blindingly bright beam to play with outside, 532nm is the way to go.
As for durability, don't buy off of e-bay, most everthing on there is junk. Go with someone on this forum in the B/S/T section. Or, O-like, rayfoss, etc.(look under company's review section to find some good ones.)
But the ones built by expert builders on this forum will be your best bet. Most e-bay seller's will ignore you if you have a problem. (most, not all)
O-like & Rayfoss are very respected here.
EDIT: I see others have beat me to it, but being as I typed it already, I'll post.LOL
