The Item Type of a Data-Field describes the type of item which is held. There are four categories:

• Data - data values, of elementary types or with simple structures;
• Samples - inventory information corresponding to biological samples held by UK Biobank;
• Bulk - large complex objects, typically binary files (blobs) which cannot be decomposed into smaller chunks.
• Records - inventory information describing the number of (records) held.

Bulk data is only available to approved researchers using special download clients - for general bulk data see Resource 644 and for genetic data see Resource 668.

Records data is available to researchers for in-situ use via the secure repository; see the guide on accessing UK Biobank data for more information.