I have had a number of different frames over the years; older frames from Eastman, etc. made from hardwoods are good if not damaged. Many frames I've gotten off Ebay have been made of soft wood, not hardwood. Soft wood is a challenge because they shed wood fibers and collect dust, which also gets onto the negative. I currently use ancient Eastman contact frames for 8x10, 5x7 and 4x6 and a new 11x15 from Bostick & Sullivan, which appears to be designed to survive the zombie holocaust.