The J-Max is the one in the 1Zpresso lineup aimed at espresso. Espresso needs small, precise changes in grind size, and the J-Max is built for exactly that, with very small steps between settings and an external adjustment ring.
It can grind for filter coffee too, but if you donβt make espresso, one of the other 1Zpresso grinders is probably a better fit. Read more in my hand grinder post.