Nothing because you also need a good pair of goggles. Before jumping into the hobby, learn how to be safe with the hobby before hand. This IS a VERY DANGEROUS hobby when people are CARELESS.
And with time learning from the forums, you will pick up on what to buy and what not to buy specifically for your needs.
What are your needs for a laser by the way?
I have the laser saftey glasses my step dad bought me a pretty powerful laser but just as i started having fun with it i dropped it and broke it so i want a new one