This new spine meter conveniently mounts on your wall and doesn't take up valuable bench space. Accurately engineered and calibrated to give spine and deflection reading equivalent to a full size spine tester. Reads 30 to100 lbs. spine and .200 to .900 inches of deflection. Works with 5/16 to 23/64 shafts. Optional 1/2 pound weight allows Ace Spine Master to read down to 15 pounds of spine for light weight kids arrows.