Product Code: XC8167451
This is the extra one supplied with the 4000D for when you want to use bobbin fill other than Brother type. If you find your bobbin thread is coming up on top of the fabric, change to this item and you should find it corrects the problem because it is tensioned higher. XC8167251. If using pre-wound bobbins use the Bobbin Raiser available in this spares section.