My WRX WR blue is pretty much standard and as such has the black side skirts, I've found a set of side skirts in the right colour, do they just secure over the black ones or are they a replacement? Will I need any additional clipage?

Cheers

 

They'll be a replacement so you'll need to pop off the clips that hold your black ones (there are clips at both ends, and underneath). You may be able to reuse the clips but i'd be tempted to replace them and then use Sikaflex/Tigerseal as well to ensure they don't move anywhere. A straightforward process, I'll be doing the same shortly too.