Most mountain bikes use an aluminum frame, as it’s light enough to not hinder maneuverability and handling while being durable enough to handle shock and rough terrain. Some high-end bikes will opt for a carbon fiber frame instead since carbon fiber is typically lighter and more durable than aluminum. That isn’t to say that you can’t find a carbon bike on a budget; the Beiou Toray T700 has a sleek carbon frame for an accessible price.