Quick tyre question

[gillywibble]

225/45R17 91Y BRIDGESTONE POTENZA RE050A 1Z

What does the 1Z mean at the end? Some also have 'BZ'.

Thanks

 

[RSClio]

OE Fitment Code/Compound

 

[RSClio]

Bit more info

Original Equipment (OE) The original brand of tyre or battery that was fitted by the car manufacturer. There may be more than one OE brand fitment.

Hope that helps.