Lenovo ThinkPad X1 Series Hardware Maintenance Manual page 63

– Optional-service CRUs: Refer to parts that can be installed or replaced by customers with a greater
skill level. Trained service technicians can also provide service to install or replace the parts under the
type of warranty designated for the customer's machine.
– FRUs: Refer to parts that must be installed or replaced only by trained service technicians. If customers
choose to replace the FRUs by themselves, the product warranty might be affected.
• Each FRU/CRU is available for all types or models, unless otherwise specified.
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Chapter 7 Locations