*** I only officially accept Eureka ultem ink cartridge as main ink storage device for my pens.
I no longer officially recognize Con-70 / Con-40 as main converter for Eureka fountain pen models.
Although they are still compatible, you must read con-70 related manuals / tips before using them.
It is tricky to get it right, although if you are skilled / experienced with the system, it is possible.
For those having difficulties , I recommend the machined ultem cartridge instead.
please note that because of the way Con-70 was produced, external surface is not consistently accurate between batches / not perfectly round.
So some of them may require "taming" by wearing the external surface down to match eureka grip part.
This is only problematic for fitting into eureka grip section, which uses external surface to seal (as opposed to internal surface).
*O-ring for the con-70 is not included with your pen.
You can use the o-ring from the ULTEM cartridge (same size)
For Con-70, O-ring is not absolutely necessary.
But if you want a secondary protection, O-ring can be purchased @ "Shop(Parts)" category.
the O-ring can be added to all products that use the 5th gen. ebonite feeder.
For additional protection you can use silicone grease @ sealing area.
