Impedance and current — the two numbers that decide fit
The BLM15HB221SH1D: This bead presents 220 Ohms at 100 MHz, the standard reference frequency for signal-line suppression. At that point the impedance is purely resistive — the inductive rise has flattened, so the attenuation is stable across the upper VHF band. The 250 mA continuous current rating is the DC bias limit. Above it the ferrite core saturates and the impedance collapses — the bead becomes a wire.
AEC-Q200 qualification means this bead passed the automotive passive-component stress tests: 1000 temperature cycles, 85°C/85% RH biased humidity, mechanical shock and vibration per the AEC-Q200 rev D profile. It is the same grade used in engine-control modules and body controllers — not just infotainment. A bead rated only to 105°C would need derating in under-hood locations; this one does not.