The flag of Montserrat is a blue ensign with the Union Jack in the upper hoist-side quadrant (canton) and the Montserrat coat of arms centered on the right half. Here are its features:

1. Aspect ratio: 1:2
2. Background color: Blue (#00247D)
3. Union Jack colors:
   • Red (#C8102E)
   • White (#FFFFFF)
4. Coat of Arms:
   • Green Hill: (#007A33)
   • Limbs of the female figure: Brown (not standardized)
   • Clothing of the female figure: White (#FFFFFF)
   • Harp: Yellow (#FCB514)
   • Cross: White (#FFFFFF)
   • Bible: Red (#C8102E) and Gold (#FFCC00)

Note that these are approximate color codes, as exact values may vary slightly depending on different sources or representations.

The flag does not have specific measurements for its elements, but their relative positions are as follows:

• The Union Jack occupies the top left quarter of the flag, extending to half of the flag's length and height.
• The coat of arms is centered on the right half of the flag.