Hi, Im not sure if this can be done, im just delving into templates so perhaps my understanding is a bit wrong. I have a Platoon of soldiers, the platoon inherits from a formation to pick up the formations properties, but because i could have as many formations as i can think of I chose to use the CRTP to create the formations, hoping that i could make a vector or array of Platoon to store the platoons in. but, of course, when i make a Platoon, it wont store it in the vector, "types are unrelated" Is there any way around this ? i read about "Veneers" which are similar and that they work with arrays but i cant get it to work, perhaps im missing something. here's some code: (sorry about the formatting, the code is here in my post but its not showing up for some reason ) template < class TBase > class IFormation { public : ~IFormation(){} bool IsFull() { return m_uiMaxMembers == m_uiCurrentMemCount; } protected: unsigned int m_uiCurrentMemCount; unsigned int m_uiMaxMembers; IFormation( unsigned int _uiMaxMembers ): m_uiMaxMembers( _uiMaxMembers ), m_uiCurrentMemCount( 0 ){} // only allow use as a base class. void SetupFormation( std::vector<MySoldier*>& _soldierList ){}; // must be implemented in derived class }; ///////////////////////////////////////////////////////////////////////////////// // PHALANX FORMATION class Phalanx : public IFormation<Phalanx> { public: Phalanx( ): IFormation( 12 ), m_fDistance( 4.0f ) {} ~Phalanx(){} protected: float m_fDistance; // the distance between soldiers void SetupFormation( std::vector<MySoldier*>& _soldierList ); }; /////////////////////////////////////////////////////////////////////////////////// // COLUMN FORMATINO class Column : public IFormation< Column > { public : Column( int _numOfMembers ): IFormation( _numOfMembers ) {} ~Column(); protected: void SetupFormation( std::vector<MySoldier*>& _soldierList ); }; I then use these formations in the platoon class to derive, so that platoon gets the relevant SetupFormation() function: template < class Formation > class Platoon : public Formation { public: **** platoon code here }; everything works great and as expected up until this point. now, as my general can have multiple platoons, I need to store the platoons. typedef Platoon< IFormation<> > TPlatoon; // FAIL typedef std::vector<TPlatoon*> TPlatoons; TPlatoon m_pPlatoons m_pPlatoons.push_back( new Platoon<Phalanx> ); // FAIL, types unrelated. typedef Platoon< IFormation< TPlatoon; fails because i need to specify a template parameter, yet specifying this will only allow me to store platoons created with the same template parameter. so i then created FormationBase class FormationBase { public: virtual bool IsFull() = 0; virtual void SetupFormation( std::vector<MySoldier*>& _soldierList ) = 0; }; and made IFormation publicly inherit from that, and then changed the typedef to typedef Platoon< IFormation< FormationBase > > TPlatoon; but still no love. now in my searches i have not found info that says this is possible - or not possible.