This lens is an EF 400mm f/5.6L USM.
Features

* Focal length and maximum aperture: 400 mm f5.6
* Lens construction: 7 elements in 6 groups
* Diagonal angle of view: 6�-10�
* Focus adjustment: Inner focusing system with USM
* Closest focusing distance: 3.5m / 11.5ft
* Filter size: 77mm

This high-performance lens was designed with portability and handling ease in mind

This high-performance lens was designed with portability and handling ease in mind.
One super UD-glass element, whose characteristics are similar to fluorite, and one UD-glass element result in sharp pictures from corner-to corner.

The lens also has a built-in hood and a detachable tripod mount.