I added a 16" pakiT to my 20"NWT. I've found for day to day city riding, errands, and exercise the 16" works wonderfully. However, I have learned the hard way that 16" wheels cannot take the same terrain differences that 20" wheels can. Without thinking I went over a section I regularly take on my NWT with zero issues, and the 16" wheels jammed and I fell. Bruised knee (protecting the bike) and ego but no issues otherwise. Lesson learned - they are not interchangeable.