These infusers are a sure thing for steeping tea in tea cups of various sizes – the wide round collar allows the infuser to fit most large and medium-sized teacups.
Retro-fitting infusers for use in teapots is a bit tricky – there are two things to consider for a good fit:
1. the diameter of the teapot opening. Will it be too narrow or too wide for the size of the infuser?
2. will the teapot lid fit down over the infuser while it is in place?