This is the Canon EF 135mm f/2L USM telephoto lens:
Sample Photos
Canon 5D Images From Italy, in B&W
Accessories and add-ons
The EF 135 f2 L USM takes 72mm filters. Recommended filter brands are B+W and Hoya.
Resources
Official Canon EF 135 f2L USM page at Canon USA.
Related
Canon Lenses – Main page