Notes: 331-8499 STUD 10.9 L88 M22x2.5x23.7, M20X1.5x50 is original CATERPILLAR product. 331-8499 STUD 10.9 L88 M22x2.5x23.7, M20X1.5x501 is commonly used in transmissions/axles/engines . if you have any questions please do not hesitate to contact us via Whatsapp +17275652849