The Volcano Barends combine the good things about aluminum and nylon options. Fly created a design with a durable CNC aluminum core and replaceable nylon rings. Since the rings are separate from the core, the bar end is able to use an extra tough nylon / fiberglass compound that gives them a long lifespan. The Volcano barends are gentle with your hands and silent when your bike does fall. Each set include a set of extra rings.