"using" keyword for base class variable

I am going over the WildMagic 5 engine (www.geometrictools.com) where the Vector<> class is inheriting from a Tuple<> class which has an array of a particular size, named mTuple[] (set by a template parameter). So far so good, nothing special. In the Vector class however, I see the following:

protected:
    using Tuple<4,Real>::mTuple; 

Now I know that the using keyword is used for inheriting overloaded methods properly. In this case, I always assumed the variable was available to the derived class without typing the above code. Is the above necessary? Or is it just there to make things clearer?