Picture frame bumpers are essential for any professional picture framing job. Place one self-adhesive bumper on each corner on the back of the frame. Bumpers keep proper airspace behind pictures, prevent scratches on the wall behind the picture, and helps prevent movement of the picture while hung. These bumpers are great for other uses as well - stick on the bottom of machinery or tools to keep them from moving around on your work table, keep doors quiet while closing, etc. These 1/2 inch diameter (12.7 mm) clear bumpers are sold in sheets of 200 - enough for 50 frames. Made in USA.