superior applied delimbing force (not theoretical) Minimal fiber damage The most accurate dual length measuring and simple and strong design Traditional models have two moving knives while LD4 and HD4 models like the 51LD4 have 4 knives/arms. This is an ideal commercial thinning tool, while the Motomit IT computer system makes operator’s job easy; just a touch of a button can process the whole tree into many different sorts.