When sourcing carbon fiber shafts, you must prioritize the modulus of the carbon fiber (Standard, Intermediate, or High Modulus) as it determines the stiffness-to-weight ratio. Key metrics include tensile strength (measured in MPa), outer diameter (OD) and inner diameter (ID) tolerances (typically ±0.05mm for high-precision applications), and the fiber orientation (0°, 45°, or 90° wraps) which dictates torsional rigidity. Ensure the supplier uses high-quality epoxy resin systems to prevent delamination under thermal or mechanical stress.