Selecting the correct unlock SIM (often referred to as R-SIM, GPP, or Turbo SIM) requires matching the ICCID/IMSI bypass technology with the specific smartphone model and OS version. You must ensure the chip uses the latest 2024/2025 decoding algorithms to bypass carrier locks on both iOS and Android. Prioritize FPC (Flexible Printed Circuit) designs that are ultra-thin (approx. 0.1mm) to prevent physical damage to the phone's SIM tray. For B2B buyers, it is essential to source cards that support 5G network stability and VoLTE functions, as older chips may only support 2G/3G, rendering them useless in modern network environments.