This is a mechanical HDD drive with a 900 GB storage capacity. The form factor is 2.5" which apart from this model is commonly used in SSD drives.
From Ecprof
ST900MP0006 - Exos 15E900 HDD 512N 15K 900GB SAS
AA2Z Supply
SEAGATE ST900MP0006 ENTERPRISE PERFORMANCE 900GB 15K RPM SAS-12GBITS 256MB BUFFER 2.5INCH 512N INTERNAL HARD DISK DRIVE. BULK. .