What features does it have to protect against theft? A 12mm thick rounded shackle which is made of specially hardened steel just like the body and structural parts of the locking mechanism. Combined with a high-quality locking cylinder which offers superb protection against tampering such as picking thanks to double locking, the Ultra Mini 410 U-Lock is a reliable companion when you are out on your high-end bicycle. The lock passed the ice spray test with flying colours.