Notes: 320-9350/GEUG65236 HEXAGON NUT UNI 5589 M16 8 is original CATERPILLAR product. 320-9350/GEUG65236 HEXAGON NUT UNI 5589 M16 81 is commonly used in transmissions/axles/engines . if you have any questions please do not hesitate to contact us via Whatsapp +17275652849