Modulus Graphite (before — Modulus Guitars) is an American manufacturer of musical instruments best known for building bass guitars with carbon fiber necks. The company, originally called Modulus Graphite, was founded in part by Geoff Gould, a bassist who also worked for an aerospace company in Palo Alto, California. The name is a reference to Young's modulus, a measure of the stiffness of an elastic material, used in the field of solid mechanics. Carbon fiber has an exceptionally high modulus.

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Phil Lesh.
Playing Modulus Quantum 6 Bass

Oteil Burbridge.
Playing Modulus Q6 Semi-Hollow Bass

Flea.
Playing Modulus Moded Bass

Mike Gordon.
Playing Modulus Quantum 5 Bass

Dave Schools.
Playing Modulus Quantum 6 Bass