Each triangle comes with a metal striker and easy-to-hold knob. Available in sizes 4″ and 6″. They have a pleasant sound and are easy for a child to grip. Great for cognitive skills such as learning how to pay attention, memory and thinking, as well as assisting to build and develop a child’s sensory skill set. This triangle is a great tool for engaging any student or classroom and great for building both sensory and cognitive skill sets.