I found about SRS suppliers on Internet. Their website it's very well set it and it's easy to make calculations. But I decided to call them. One thing which I very much liked it that they didn't pretend to be friendly I felt actually that they are friendly. I received very good service, and all the materials for my roof arrived on time as was promised . I myself in the business I am electrician, I'm not a roofer but I decided to do my roof for my shed on my own, the good thing about this company they advised me they spend time with me. And they never forced me to buy their products. They are great.