ACML-0402H-121-T Substitution Conclusion The ACML-0402H-121-T can serve as a direct replacement for the original part number BK1005HS121-T. This is based on identical core electrical performance—impedance at frequency, rated current, and DC resistance—as well as matching package dimensions. Consequently, its filtering effectiveness and basic current-carrying capability within the circuit will be fully equivalent. Two minor technical differences exist between the two parts. First, the ACML component has a slightly greater profile height (0.65mm vs. 0.55mm). This height difference is unlikely to cause interference in the vast majority of 0402 footprint mounting scenarios. However, verification is recommended for designs with extreme component stacking or exceptionally tight vertical clearance. Second, the ACML variant is explicitly designated as a "Power Line" type. This suggests its magnetic core material and performance may be optimized for power line noise suppression. In contrast, the original part is presented as a more general-purpose component without such a specific designation. This difference implies the ACML part may offer more reliable or targeted performance in power rail filtering applications, though it does not affect the fundamental rated specification of 120Ω @ 100MHz. In summary, the substitution is electrically and mechanically viable and can be implemented.