That laser will probably be far from 300mw, you would have to be very lucky to get a 300mw green laser at that price. I would've bought a 200mw from o-like/beamcheap or rayfoss instead, their lasers are more likely to be up to spec and they have better customer support.
You always take a gamble with focalprice, that thing could also be mostly IR, so while you may think "all I got for 150.00$ is a 5mW green??" it could very well be an invisible spotlight of blindness... If I were you I'd definately take a closer look at olike/beamcheap and rayfoss before purchasing that.
OK, I keep seeing people promoting this website. Fact, there has not been enough experience with this company to say anything. Please stop saying this company is a good company till we have more reviews and info.