Hardened steel, 3mm thickness. Easy to fold due to several pivots . Plastic cover to protect the frame .Compact, easy to transport on a bicycle .Universal transport bracket for frame or bottle holder. 2 Key, security level: 5 (of 10). Lifetime Warranty,free key-safe program: After registering the key number on www.kryptonitelock.com the first 2 replacement keys are free in case of loss. Optional Anti-Theft Protection Offer with Euro 400.00 coverage (only valid for online registration within 30 days after purchase). Detailed conditions of participation at www.kryptonitelock.com.