These are official spare parts compatible with the UltiMaker Factor 4.
$169.00
A genuine 'BB' style Ultimaker Print Core with a 0.8mm nozzle, for printing PVA support material.  Compatible with the following Ultimaker printers: Ultimaker 3 Ultimaker 3 Extended Ultimaker S3 Ultimaker S5 Ultimaker S7 UltiMaker Factor 4