The flag of Brunei has a yellow field with two diagonal stripes, white over black, in the canton and a red crest centered on the yellow field. The aspect ratio is 1:2.

Color codes:

• Yellow: Pantone 116 C (#FFCD00)
• White: Pantone White (#FFFFFF)
• Black: Pantone Black C (#000000)
• Red: Pantone 186 C (#CE1126)

Geometric properties and measurements:

• The flag's width is divided into four equal horizontal stripes (two yellow, one white, and one black).
• The white stripe is placed directly above the black stripe, forming a parallelogram with vertices touching the top-left corner, bottom-left corner, and midpoints of the top and bottom edges.
• The red crest is centered on the yellow field, and its height is 3/5 of the flag's height.

For more specific measurements, please consult official sources or guidelines for the flag of Brunei.