Too bad that after I removed the fuel filter, I've noticed the new one is incompatible since it has different inlet and outlet tubes - the clamps can't secure it.

 

However on the product page for both filters it lists my 1.6 MK3 as compatible. How can I know for next time?

 

The one on the LEFT looks like the correct one.

 

The other looks to be some sort of 'universal' fitting, the photograph appears to show a smaller and large diameter before/after the  swaged part, so maybe it would fit if the flexible hoses are long enough to accommodate it.

Actually the one on the right was (and still is) installed on my car. The one on the left was ordered online after insuring my model was listed on the product page, but eventually it can't fit the tubes.  

Ok mystery solved

The one on the left (short tubes) is aftermarket for 6N0 201 511 A and the one the right is 6N0 201 511 B...

I do not know what each is used for though.