666986-B21: HPE Large Form Factor Hard Drive Blank Kit (675039-001)

666986-B21 is HPE's large form factor (LFF) hard drive blank kit. PartSurfer maps it to spare 675039-001, described as a hard drive blank (cover) that fills empty LFF drive bays. It is a plain cover with no electronics.

The distinction that matters at ordering is bay size. LFF means 3.5in bays. The sister kit for 2.5in bays is a different option, 666987-B21, whose PartSurfer spare 670033-001 is described as a blank for small form factor bays in Gen8 servers. The two are not interchangeable, so measure or count the bays on the chassis first.

Server fit is not stated for this spare. HPE's DL380 Gen10 QuickSpecs says factory-built servers ship with enough drive blanks for the drives that were not ordered, and it describes 8LFF and 12LFF chassis, but it does not list 666986-B21 or 675039-001. For a DL380 Gen10, or any current-generation chassis, compare the blank in the existing bays with 675039-001 by its latch and tray shape rather than assuming a match from the option name.

Related blanks on the site: 666987-B21 for SFF bays and P07818-B21, the DDR4 DIMM blank kit that the same QuickSpecs requires on empty DIMM slots of the DL380 Gen10. Chassis-side parts are under the HPE and other server parts hub.