I built an MDF drawer unit using 18mm and they were just over 1m wide and 25mm high and the rails held them no problems.
I did buy rails screws but they were bigger than the holes predrilled in the rails so had to make them bigger, i could only find 2 sizes and they were the smallest, other than that really easy to fit."
"An absolutely excellent product at a price normally paid for very much infereior "equivalents". Capable of supporting a fully laden tool draw, approx. 150kg, without difficulty. Smooth running and easy to install. I recommend this high quality product without reservation."
"These were bought to convert fixed shelves in a larder unit. They did a great job. Very easy to fit and very robust. The shelves are now easy to slide out, and with the amount of weight on them there is no fear of any of the shelves collapsing. Very pleased."