The Kana Extended-B block spans U+1AFF0–U+1AFFF, 16 codepoints in Plane 1 (Supplementary Multilingual Plane). 13 are assigned in Unicode 16.0; the other 3 are reserved for future characters.
All of its characters belong to the Katakana script.
By general category: 13 modifier letters (Lm).
The first 13 arrived in Unicode 14.0 (2021).
13 characters are East Asian Wide or Fullwidth and take two columns in terminals.
Because it lies outside the BMP, every character here takes four bytes in UTF-8 and a surrogate pair in UTF-16.