The author defined them as all hills within the boundary of the Lake District National Park in Cumbria which are over 1,000 feet (304.8 m) in height.

[4] Because both lists are based on historical books, unlike for example the Murdos, their constituents remain fixed, regardless of revisions to height or other metrics.

The Long Distance Walkers Association maintains a register of people who have completed the Birketts.

[7] 54 of the 514 peaks are solely Birketts, and meet no other mountain or hill classification in the British Isles.

The DoBIH uses the following codes for the various classifications of mountains and hills in the British Isles, which many of the above peaks also fall into:[11][12]