Notes: 1990759 - p/o 20237 O-RING 4850 215.49x3.53 is original CATERPILLAR product. 1990759 - p/o 20237 O-RING 4850 215.49x3.531 is commonly used in transmissions/axles/engines . if you have any questions please do not hesitate to contact us via Whatsapp +17275652849