Dyson compatible DC04 brush bar (clutch models only)

When would this part need replacing?
When the bristles are worn
Brushbar seized (not spinning freely)
Not picking up as well from the base

Fits the following clutch models:
DC04 Absolute, DC04 Absolute Purple Lime, DC04 Brush control, DC04 De Stijl, DC04 Limited Edition, DC04 Zorbster.

Compatible Dyson DC04 brushbar clutch models only