Z-hop height (mm)

The Z-hop height is the extruder lift up height when moving between print areas. Choose minimum for fast printing process, but enough for prevent part edges hitting and as a result bringing and leaving beads on a part shell. Z-hop may lead formation of strings, however, it is usually easier remove this than removing beads.

Extra unretract length (mm)

The extra unretract length is the value additional to retract length. On print resuming, if portion of plastic has spilled from an extruder, then volume of plastic in a nozzle becomes less than what it was before travel. If you have noticed for this plastic (especcially for runny) that at the beginning of print there is an underextrusion migrating to normal extrusion, then you shoud set not null for this parameter.