The SECOND HAND Yuasa International Big High Speed Multiplier Spindle is a high-speed spindle speed multiplier device used to mechanically increase the existing main spindle speed of a milling machine. Made in Japan (Model ST. NO. 521-721), this heavy-duty unit features a maximum capacity of 1/4" and comes equipped with its original fitted wooden storage case, collets/arbors, and service wrenches for precise metalworking setup.