The Core attachment for the Modular system is the piece that brings all the attachments together and offers a whole new dimention in training. Slide this on to a barbell end and use it in the leverage Core position to make ALL the Modular Plug Ins a whole different beast. This is one of my favorites. I've been using the prototype for quite a while and finally have made it available to you. I promise it will open a plethora of new exercises and angles to work with.