The DD technology version requirements are defined in the Device ITK Profile Specification.
You must provide both DD4 files (extension .ffo) and DD5 files (extension .ff5). The DD5 files are a requirement for registration to the current and future H1 ITK. Each set of DD files will be tested separately using the DD related test cases.
DD6 files are currently optional and are reserved for FDI Device Packages. Please refer to FDI Device Package Registration Timeline and Requirement Update for more information about this requirement.