Khyber Knives were ubiquitous along the North West Frontier. The blades could be as long as 25 inches.
Rudyard Kipling mentions one in his The Ballad of East and West when he describes a meeting between a tribal chief and a British officer discussing a stolen horse:
They have looked each other between the eyes, and there they found no fault,
They have taken the Oath of the Brother-in-Blood on leavened bread and salt:
They have taken the Oath of the Brother-in-Blood on fire and fresh-cut sod,
On the hilt and the haft of the Khyber knife, and the Wondrous Names of God.
The picture below gies a sense of scale of the knife:
