Double consonants or a pause in speech
(e.g., /kk/, /tt/,
/pp/, /ss/)
are represented by a small (half-height) katakana ッ as shown below.
ホッケー
/hokkee/ "hockey"
Exception: Like the hiragana character
ん, the katakana equivalent ン
/nn/ is NOT considered as double consonants.
As a result, ッ is not used to transcribe this sound. See below.