compare some red laser. and hope the conclusion here can help some beginners 4 laser

here is a picture taken by one of my customers. he is new for laser. here, I may help some beginners for lasers by this picture
you can see that there are three lasers. the left one is a 5-10mw red laser point--price about 2.5-4usd. the middle is a 90mw-110mw red laser module (lenslastic, housing: brass, price:8-9usd), the right one is a 50mw red laser point--price about 15usd (I do not know the lens).
1. Concentration/coherant is the most important issue to judge a laser. simply to say, the thinner/smaller laser beam it is, the better quality is because it can reach further, can release higher heat and better burning effect.
from the picture you can see that the left laser give the biggest laser beam. the right laser pointer is the second bigger beam, and the middle is the smallest.
2. I have label some number in the picture. the laser was reflected from a wall. here I will explain them:
1: the 10mw red laser gets biggest beam,
2: nearly no reflected light on the ground.
3: smallest laser beam and best concentration, halation because of the plastic lens. if we change it for glass lens, we can 98% reduce the halation light.
4: strongest refected light on the ground
5: second biggest beam
6: second strongest refected light
3. only when the laser get laser beam as small as possible, the laser can reach very long distance.
4. only when the laser get small beam, the heat it can release and even it can burn things.
5. but some people think the bigger laser beam it is, the brighter they feel by their eys. but if they compare them for the distance, the thinner laser can reach much more further than bigger-beam lasers.
normally, big beam laser was used for stage lighting. thinner beam laser can be used for stage lighting and other areas.
this is a simple conclusion. I will use this conclusion in our ebay store. hope it is useful for other people.