Johnny C

Be carefeful with any cheap laser. If it's a 2nd hand ex-lab laser or similar then fine. But a lot of cheap high-powered lasers from China aren't safe. They produce a lot of infrared which isn't focused or filtered, so if you look along the beam and close to it or are using mirrors you can get a lot of IR in your eyes which isn't good for them, get enough and you'll start to microwave the nerve endings. Nerves don't like being microwaved...

For example, a 50mW might be a 1watt IR diode with a crystal stepdown to convert some of the IR to visible light - but a lot of the unconverted IR gets through.

I get mine built in Canada and shipped over, I pay a lot more than £20 but I know it's been tested for IR leakage (and a lot more).

Editted to add, got assorted lasers (red and green) upto 460mW. Had to stop playing so much since a visit from the old bill for pointing one a a block of flats 5 miles away and scaring some pensioners, and these days with kids pointing them at planes the police helicopters get upset at people playing lightsabers in their back garden. Still like to annoy the neighbours cats though!