KitchenAid 'C' Style Dough Hook Fits 5QT Bowl Lift Mixer. 

This Dough Hook is approx 18.5cm long

This item is a Genuine Kitchenaid Spare Part  K5ADH, 9707672, W10674621

The Dough Hook fits models that begin with.....

3K5SS, 4K5SS, 5K5SS, 5KSM5, 7K5SS, 
9KSM5, K4SS, K5SS, KDM5, KP50, KPM5, 
KPM50, KSM5, KSM50, KSMC5.

Thanks for looking.