Seagate Exos X18 18TB enterprise hard drive, model ST18000NM000J (P/N 2TV103-002). SATA 6Gb/s, 7200 RPM, 3.5", 256MB cache, helium.
Used and fully working. Every drive reports Good health with 0 reallocated, pending, or uncorrectable sectors and 0 CRC errors.