The Lamy Z27 replaced the Z26 as the universal fountain pen converter for Lamy pens. It’s the one included in higher-end pens like the Imporium. The converter has a black top and uses a screw mechanism.
Note that the Z27 is still often sold as the Z27 since the two are so similar and are difficult to tell apart. Functionally the seem to be the same but time will tell if a difference exists. The Z26 was phased out in late 2017.
Read more about this and other Lamy fountain pen converters in our explainer article.
Lamy Z27 Fountain Pen Converter Information