Before revision: Two sizes exist: "Zone 1" dishes are issued in southern England and were 43 cm vertically prior to 2009; newer mark 4 dishes are approximately 50 cm "Zone 2" dishes are issued in elsewhere (Wales, Northern Ireland, Republic of Ireland, Scotland and northern England), which are 57 cm vertically.
After revision: Two sizes exist: "Zone 1" dishes are issued in southern and Northern England and parts of Scotland and were 43 cm vertically prior to 2009; newer mark 4 dishes are approximately 50 cm "Zone 2" dishes are issued in elsewhere (Wales, Northern Ireland, Republic of Ireland, Scotland and northern England), which are 57 cm vertically.