The best on-line double glazing site I've seen to date, and makes it simple to understand how to specify doors and windows. Competitively priced and clear guidance given if you stray outside of design parameters. There are a few querks however that could be improved upon such as - 1) being able to edit items already in cart instead of having to add modified item then delete old item. 2) being able to add name identifiers to doors, windows can already have name identifiers. 3) I noticed that when you go "back" to your cart using the browser back command, duplicate items are added to the cart mysteriously, eventually warning you of "too many items in cart" if you do this too frequently.