Who can I contact for sizes?

Based on your original question about the size of a ND 511 F7 Steel window frame, I would recommend contacting the seller directly via the contact details on the product page for more information on frame size options. The search results I provided include some similar window frame and safety glass products, but to get exact sizes for the frame you're interested in, speaking to the seller is the best way to go. Please let me know if you need any other details, I'm happy to search further on PriceCheck to try and help find the right size for your needs.