when new, installing converter feels quite tight.
this is to ensure leakproof seal, for years and years.
when worn down a bit, this will become much easier.
When installing/removing ink converter on grip section, a bit of twist will make the process easier.
slight wiggling achieves the same effect.
you can install/remove in straight motion without twist/wiggling, but it will require more force (unless the parts are worn down a bit)