The target area is only 2 meters wide.
4 seconds sound clip from the Star Wars: Episode IV - A New Hope (1977) movie soundboard.
You can hear this line at 01:40:22 in the Blu-ray version of the movie.
Quote context
[...]
- Pardon me for asking, sir, but what good are snub fighters going to be against that?
- The approach will not be easy.
- You're required to maneuver straight down this trench and skim the surface to this point.
- The target area is only 2 meters wide.
- It's a small thermal exhaust port right below the main port.
- The shaft leads directly to the reactor system.
- The shaft is ray-shielded, so you'll have to use proton torpedoes.
[...]