The lock body is chrome-plated Solid Hardened Brass, and the shackle is a boron alloy for special hardness and resistance to cutting tools. (The shackle is 2" long and is 8 mm thick.)But the really special security factor comes from the unique keys. They cannot be copied by any locksmith, so you can have high confidence that the keys that you have are the only ones that are going to open the lock.
Each lock will come to you with a unique registration number for the two keys provided, and will come with instructions for a simple, yet fully secure, process for acquiring additional keys from the lock maker. The cost of a lock should be proportional to the value of what you are securing. If what you are locking up is not particularly valuable, we advise that a less expensive lock be used.