Selling things that may be used for haraam purposes
Question

                My brother has a store that sells and installs radio systems, car t.v.'s alarms, tints on windows, big speakers,and amplifiers. Is this kind of business halaal?

We are in america and mostly teenagers would buy these type of things to make their car look nice and to make their music loud.
Praise be to Allah.
    If it is known that this business will help these customers to engage in evil things and promiscuity, and that they will be used to listen to songs and music, then it is not permissible to sell these things to them. But if it is possible that they may be used for permissible things and it is not known that the purchaser will use them for haraam things, then there is nothing wrong with selling them or dealing in them. If he sees someone who seems to be decent and respectable, he may sell to him, and if a customer comes who appears to be promiscuous or an evildoer, he should refuse to sell to him.