2AK30 X 15 mm Bore, 5 mm key way. This pulley is used on the 1500W. It is not for the 550, 750 or 900. This is because if your machine needs this pulley, it also needs the larger motor. Look at it this way: A chevy small block has the ability to produce 700 HP. However if you were to use it in a semi truck, it would be overworked and fail in short order. It's just not desingned for this type of duty cycle. Same goes for replaceing the giant induction motor with a servo motor. Also, I am charged a 3% processing fee when you order. In order to issue a refund, I am charged 3% again. That means if you order the pulley and a motor and I have to cancel it. There will be an $18 cancelation charge. If it's shipped and returned that loss of your shipping and refund becomes $78.00 For this reason, please contact me and ask about suitability before you order.