The Cyrillic Extended-C block spans U+1C80–U+1C8F, 16 codepoints in Plane 0 (Basic Multilingual Plane). 11 are assigned in Unicode 16.0; the other 5 are reserved for future characters.
All of its characters belong to the Cyrillic script.
By general category: 10 lowercase letters (Ll), 1 uppercase letters (Lu).
The first 9 arrived in Unicode 9.0 (2016); later additions came in 16.0 (2).