These main studs are specific for the 06a blocks. Make sure you have the correct studs for the application as the 058 studs found in earlier 1.8, 2.0, 8v, 16v, 20v engines are shorter and will not allow you to engage enough threads to properly fasten the crankshaft. These studs are for all 1.8t motors from 99.5+ mk4 1.8ts and 2.0L 8v as well as 2001+ audi a4 and passat with 1.8t engines. We recommend using these studs on any 1.8t engine making in excess of 500whp, we have made over 650whp on stock main bolts without failure, but we do not recommend it for extended use. ARP hardware is reusable, factory hardware is not, if you are building a powerful car, go with the ARP hardware and save yourself the hassle, buy the parts once and dont be stuck with replacing stock bolts and costly replacement.