Lenovo ThinkPad X1 Carbon Hardware Maintenance Manual page 50

– Optional-service CRUs: These CRUs are isolated parts within the computer that are concealed by an
access panel that is typically secured by more than two screws. Once the access panel is removed,
the specific CRU is visible.
• A Self-service CRU is identified by a single asterisk (*) in the CRU ID column. An Optional-service CRU is
identified by two asterisks (**). An N in the CRU ID column means that the part is not a CRU.
• FRUs marked with OP
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Hardware Maintenance Manual ThinkPad X1 Carbon and X1 Yoga
are available as options.