These Hopkins "Graduated Levels" come two to pack and are exactly what we needed for our new "pop-up" camper. These can be installed using the included double-stick tape or, more permanently, using the two pre-drilled screw holes (screws not included). We opted for the double-stick tape option since I really didn't want to put holes in my camper walls.These levels are easy to read from a distance and are very accurate.Highly Recommended!CFH