No more guesswork to find the center of the circle. It is made of high quality aluminum. Without a ruler, the red aluminum piece weighs 7.2 ounces. Ruler 12 inches, millimeter markings on the back. Be sure to correct any alignment issues by loosening the screws and pressing the ruler against the wall of the plate, then retighten. Mine arrived a little crooked with the ruler from not pressing it against the wall. Nevertheless, it's 5 stars!