This water-based GREY primer is both a Gripping Primer as well as a Stain-Blocking Primer! 

The grey colour is great as a base for bright colours. You'll need fewer coats of bright colours if you start with a grey base - it's got to do with light absorption and scattering ;-p

No more confusing yourself over which primer to use as this one does both jobs of gripping and blocking! :-)

Also available in White.