A 10.5" Putti bone rasp – 18mm to 4mm is a surgical instrument used for bone shaping and smoothing, particularly in orthopedic and reconstructive surgeries. The 10.5" refers to the overall length of the rasp, while the 18mm to 4mm indicates that the blade tapers from 18 millimeters in width at the base to 4 millimeters at the tip.