The Fineline 0.4mm / 126844 nozzle set has now been discontinued by the manufacturer.
The 126844 nozzle set has been replaced with the 0.45mm Fineline / 712364 nozzle set, this is fully compatable / interchangeable with the 126844 nozzle set & offers improved performance over the original 0.4mm set.
The 0.45mm Finleine / 712364 nozzle set can be found HERE