Lenovo SYSTEM BOARDS 5B21P15405 is compatible in the following Models:

Lenovo ThinkPad X Series laptops

ThinkPad X12 Detachable Gen 2 (Type 21LK, 21LL) Laptops - 21LKCTO1WW
ThinkPad X12 Detachable Gen 2 (Type 21LK, 21LL) Laptops - 21LLS1J707
ThinkPad X12 Detachable Gen 2 (Type 21LK, 21LL) Laptops - 21LLS7G400