With 3 in 1 Forillon Photo Frames, you get three sizes in one. They feature aluminium moulding for lightweight, elegant, modern and durable framing. Quality frames that blend in seamlessly into any home or office decor.  Sizes 8 x 10", 5 x 7", 4 x 6", 12 x 18", 8 x 10" and 5 x 7" have glass panes, while larger sizes have plexi panes. Additional information: What is a mat? A mat is a piece of cardboard (usually with an opening in the centre) that leaves a space between the photo and the frame. It is only suitable for paper artwork, not canvases. When a mat is used, there is usually a glass panel to protect the photo and the mat. Finally, when you see the words "acid-free or conservation", it means that the mat is archival quality and will not fade, yellow or alter the work over time.