Suit GQ TB42 Motors
There are 2 sizes of Fan Blades to suit the GQ TB42.

The early ones are supposed to measure 101mm from one mounting hole to the next
(the bolts that mount the blades to the viscous hub)
the later ones (Typically EFI) are supposed to be 95mm from one bolt hole to the next. 
However this is not a very solid rule, and can very regularly be incorrect.
the safest method is to measure yours before ordering.
These ones are the Smaller Bolt spacing (95mm) to suit the Later Model Engines From 1991 On

The Plastic Fan Blades on the Front of your engine can Perish and Crack over time.
if your fan Blades have cracks appearing it is a Good Idea to change them before they explode.