Mountain High 515l (CFF-480) Carbon Fiber Filament Cylinder
The Mountain High Silica (glass) fiber-wrapped cylinder (CFF) have an aluminum core with a fiber wrap. They are DOT-E 7277-3000 rated.
Carbon fiber cylinders are lighter than aluminum and a little more expensive. In Europe, the CFF-480 can be compressed up all the way up to 3000 psi, meaning more significantly more available oxygen. Carbon fiber cylinders have a service life of 15 years (if they pass hydro testing every 5 years), after which they should be retired. One exception: the CFF-480 requires testing every three years.