Accessing typedef's/using's of template parameter

Question

I'm currently working on a templated mathematical vector class. While doing so I came across some irritating behavior.

My actual vector class is inheriting the components from another class via a template-parameter (because my components are a union of an array and individual variables (x, y, z)).

I wanted to access the value_type of the component class via a using-declaration. But this yields an error indicating, that the identifier is unknown. Is it illegal to access using-declarations of template parameters? And what would be a nice workaround?

Code example to clearify:

#include <iostream>

template<typename T, size_t N>
struct Components
{
public:
    using value_type = T;

    constexpr static size_t getDim() {return N;}


    union
    {
        T arr[N];
    };
};

template<class COMPONENTS>
struct Vector : public COMPONENTS
{
    COMPONENTS::value_type mag()
    {
        return 22.f;
    }
};

int main()
{
    Vector<Components<float, 3>> vec;
    vec.mag();
}

Thanks in advance, Luis Wirth.