BTI L20C4P71-BTI 15.44V 57WHR LI-ION BATTERY FOR THINKPAD X1 CARBON GEN 10, X1 CARBON GEN 10 21CB, X1 CARBON GEN 10 21CC, X1 CARBON GEN 11, X1 CARBON GEN 11 21HM, X1 CARBON GEN 11 21HN, X1 CARBON GEN 9