High Security - Durable 16mm diameter steel shackle resists cutting, tampering, and lifting Easy to Carry - The lock doesn't take up much space, making it easy to store and carry. With the mounting bracket, you can install the U-lock on your bike. High Quality - The U-lock, with its PVC cover, resists corrosion from water, dust, and dirt, thus extending its lifespan. Convenience - 2 keys for added convenience! The U-lock comes with 2 keys. You can use one daily and leave the other at home in case you accidentally lose the key.