M63 is a NiZn ferrite with an initial permeability (μi) of approx. 180, a saturation flux density (Bs) of approx. 365 mT at 25 °C (290 mT at 100 °C) and a Curie temperature above 300 °C. It keeps losses low at a mid-high permeability (loss factor 50×10⁻⁶ at 0.5 MHz / 80×10⁻⁶ at 5.0 MHz) while holding Bs at 365 mT and Tc above 300 °C — a balance of permeability, loss, flux and temperature that makes it the general-purpose workhorse for low/mid-to-HF power inductors. As an EMI-suppression material its normalized impedance is measured on an RH5×1.5×10 bead (curve on the next page). Typical uses are low/mid-to-high-frequency power inductors, RF filters and energy-transfer modules in industrial electronics. In the ladder it sits between M61 (μi approx. 100) and Q1C1 (approx. 250): go to M61 for a higher frequency ceiling, to Q1C1 for higher inductance density (at a lower Curie temperature, >140 °C).