To help the community define properties, we are releasing a set of 168 pre-built properties that can be used to guide Echidna, our smart contract fuzzing tool, or directly through unit tests. Properties covered include compliance with the most common ERC token interfaces, generically testable security properties, and properties for testing fixed point math operations. As a bonus, while creating and testing these properties, we found a bug in the ABDKMath64x64 library: for a specific range of inputs to the divuu function, an assertion could be triggered in the library.