1. BK1005HS121-T Substitution Conclusion The BK1005HS121-T can serve as a drop‑in replacement for the original part GZ1005U121CTF, as their key electrical parameters are fully aligned: both exhibit an impedance of 120 Ω at 100 MHz, a rated current of 500 mA, and a maximum DC resistance of 200 mΩ. The identical package size (0402) ensures equivalent filtering performance and current‑handling capability in the circuit. The differences lie in the maximum height (0.55 mm for the BK1005HS121‑T versus 0.65 mm for the original) and the Filter Type designation (the original is specified as “Signal Line,” while the substitute does not specify a type). The reduced height may offer an advantage in space‑constrained PCB layouts, though mechanical clearance during assembly should be verified. An unspecified Filter Type generally indicates that the substitute is suitable for general‑purpose signal‑line filtering, which remains compatible with the original application. The manufacturer change from Sunlord to Taiyo Yuden may introduce supply‑chain or cost variations. However, Taiyo Yuden is a well‑established supplier with typically higher reliability. Therefore, the substitution is technically viable. It is recommended to validate mechanical fit and procurement feasibility in the actual application.