About this product The 7-rib drive belt 7PJ451 is compatible with Bosch Rotak 320 lawn mower. 7PJ451 rubber drive belt for lawn mower with closed loop, width 16mm and circumference 451mm with 7 ribs. The replacement 7-rib drive belt is made of rubber, more wear-resistant, durable and flexible. Perfect replacement for your damaged or worn belt. Before purchasing, please check the model and double check the size of your old belt.