Here's the classic way to study force and vectors. Our lightweight, accurate device has a performance that exceeds the degree of accuracy needed for most high school or college applications. Our 16" (40 cm) diameter masonite disc balances on our sturdy cast-iron tripod base. The disc has a permanently printed decal with large, easy-to-read numerals. It is graduated in two 360° scales to prevent parallax error. The weight harness snaps into place around a central ring. The base can be fine-tuned with leveling feet. We include 4 work-horse low-friction pulleys with low 0.04 Coefficient of Friction. Includes: 4 pulleys; 4 slotted "use anywhere" weight hangers; tripod base; force table with two scales; instructions with theory and sample problems. You need slotted weights, not included.