How fast a putt rolls on a green, measured with a Stimpmeter — a simple metal ramp that releases a ball at a known speed; the distance it rolls in feet is the green's "Stimp" reading. A typical public course runs 8–10; PGA Tour greens hit 11–13, and Augusta's are rumored near 14. Why it matters: the same putt needs a much softer stroke on fast greens, and downhill putts get scary. Check the Stimp before you play and adjust your pace early.