I ordered the frame with a 18x24" picture size. I called prior to ordering to confirm that the mat worked with an 18x24" poster. They ensured me that if it says 18x24" for the picture size then it will fit. Of course when it arrived the frame was roughly 18.5 x25" and the hole in the mat was only 11.5 x 17.5". Frame is okay, and the setup was easy. Just wish they wouldn't allow you to pick the "picture size" and ensure you that it will fit an 18x24" poster when it definitely does NOT.