Cura/resources/extruders/blocks_r21_extruder_0.def.json

{
    "version": 2,
    "name": "Extruder 1",
    "inherits": "fdmextruder",
    "metadata":
    {
        "machine": "blocks_r21",
        "position": "0"
    },
    "overrides":
    {
        "extruder_nr": { "default_value": 0 },
        "material_diameter": { "default_value": 1.75 }
    }
}