| Fiber Class | Diameter (µ) | Velocity | Effective Stimuli |
|---|---|---|---|
| Aβ (myelinated) | 12–20 | Group II (>40–50 m/sec) | Low-threshold mechanoreceptors Specialized nerve endings (Pacinian corpuscles) |
| α-δ (myelinated) | 1–4 | Group III (<40 m/sec) | Low-threshold mechanical or thermal High-threshold mechanical or thermal Specialized nerve endings |
| C (unmyelinated) | 0.5–1.5 | Group IV (<2 m/sec) | High-threshold thermal, mechanical, and chemical Free nerve endings |