[Where has the Hardness slider for brushes gone?]

I cannot alter the hardness of my brushes and this is most annoying. In the past when I had the Brush selected it also had the hardness slider but it hasn't anymore. This'll make blending and shading a lot harder without it. How can I put the Hardness Slider back on the toolbar as all the tutorials I have read so far indicate that it should be there. 

I have turned on anti-aliasing and upgraded to the latest version but I still haven't got it back.

Any help is most appreciated.

 

Thanks in advance