it is a frame-mounted immobilizer. Widely used in Europe, frame locks such as the Amparo are gaining popularity in the US for bicycle commuters riding dutch-style and cargo bikes. The Amparo is lightweight and works by immobilizing the rear wheel rather than locking it to a fixed object. For added security the Amparo 4850 can be used with a special ABUS accessory cable or chain that integrates into the frame lock. It is highly recommended that the Amparo be used with a second lock and not as a stand-alone security option.• 8.5mm steel shackle
• The case, shackle and supporting elements of the locking mechanism are made of special hardened steel
• ABUS patented "push'n lock" closing mechanism makes attaching accessory chain or cable a snap
• Extra large aperture
• Two keys supplied with the lock