Originally posted by nizee
They are just longer. 
Not forgetting slightly softer and more progressive too
That is why this makes the pre-tension spring a little bit redundant.
If you're using the older set of springs, then probably the pre-tension spring would help in the rear suspension. Else, the Veteq springs alone would be enough to achieve the progressive suspension needed.
I have my Impulse with the black pre-tension spring + red rear spring (27 mm) while the 705 has the red rear Veteq springs (30 mm) only. Both mounted on the rear bearing blocks and they both perform similar.