Frame is all alloy/Carbon, modified Big Hit that has been stiffened and strengthened by the addition of 3k Carbon fibre. Most of the hollow areas of the original frame have been filled in, as well as wrapping Carbon tow (think thousands of strands of carbon fiber running parallel in a rope) around the head tube and down along the frame tubes, Overkill I suppose but I did drill 2 big holes in the down tube by head to hide my wiring and cables. All alloy was coated in resin to avoid corrosion issues later on.