1: PC or APC type 2: Simplex or Duplex 3: Different types of ... ceramic sleeve, metal housing, red color dust cap (1 piece type) 2, FC/PC SM Simplex, ceramic sleeve, metal housing ... , red color dust cap (2 piece type) 3, FC/PC SM Simplex, ceramic sleeve, metal housing ... , red color dust cap (Big D type) 4, FC/PC SM Simplex, ceramic sleeve, metal ...