British letter boxes are mainly classified into 3 types: Pillar Boxes, Wall Boxes and Lamp
Circumference
Cap: 79 inch
Carcass: 61 inch
Base: 64 inch
Circumference
Cap: 66/63/65 inch
Carcass: 49 inch
Base: 52 inch
Circumference
Cap: 109 inch
Carcass: 91 inch
Base: 95 inch
Width: 20 inch
Height: 47 inch
Depth: 19 inch
Width: 13.5 inch
Height: 33 inch
Depth: 12 inch
Front Width: 13.5 inch
Front Height: 32.5 inch
Rear Width: 12.5 inch
Rear Height: 31.5 inch
Depth: 13 inch
(Made in Hong Kong)
Width: 17 inch
Height: 32 inch
Depth: 10.5inch
Width: 10 inch
Height: 24 inch
Depth: 13.5 inch
Reference: Lee, S. C., & Wu, K. K. (2015). A ramble about Hong Kong letter boxes. Hong Kong History Study Circle.