The Katakana Phonetic Extensions block spans U+31F0–U+31FF, 16 codepoints in Plane 0 (Basic Multilingual Plane). Every one of them is assigned in Unicode 16.0.
All of its characters belong to the Katakana script.
By general category: 16 other letters (Lo).
The first 16 arrived in Unicode 3.2 (2002).
16 characters are East Asian Wide or Fullwidth and take two columns in terminals.