The Extratech set for the ICM I-16 is a curiosity. While it does contain parts that are helpful with adding interior to the kit, it leaves out a lot that should be in a photoetch set. Still, there are parts that are unique to this set, namely the shoulder harness (actually the most accurate I-16 shoulder harness to date) as well as the bulkheads. However, the things that ICM missed, namely the sidewall detail and all pieces on the sidewall, are missing.
Be that as it may, couple this set with the Part photoetch set, and you have an awesome interior for the ICM I-16. Note: while Extratech specifically lists this set for the Type 24, it will also work for the Type 28 and Type 18 just as well. Now to track down the ACE photoetch set, and see how that compares to the Extratech and the Part sets.