The EF 100-400mm 4.5-5.6L IS USM is a professional EF mount

Canon EF lens mount

Introduced in 1987, the EF lens mount is the standard lens mount on the Canon EOS family of SLR film and digital cameras. EF stands for "Electro-Focus": automatic focusing on EF lenses is handled by a dedicated electric motor built into the lens...

 telephoto zoom lens

Zoom lens

A zoom lens is a mechanical assembly of lens elements for which the focal length can be varied, as opposed to a fixed focal length lens...

 introduced by Canon Inc.

Canon Inc.

is a Japanese multinational corporation that specialises in the manufacture of imaging and optical products, including cameras, camcorders, photocopiers, steppers and computer printers. Its headquarters are located in Ōta, Tokyo, Japan.-Origins:...

 in September 1998. It is a high performance tele-photo lens ideal for sports and wildlife photography which has received high ratings from purchasers at Amazon.com

Amazon.com

Amazon.com, Inc. is a multinational electronic commerce company headquartered in Seattle, Washington, United States. It is the world's largest online retailer. Amazon has separate websites for the following countries: United States, Canada, United Kingdom, Germany, France, Italy, Spain, Japan, and...

 and B&H Photo Video
.

This lens is compatible with the Canon Extender EF

Canon Extender EF

The Extender EF lenses are a group of teleconverter lenses made by Canon. These lenses are used between any compatible EF type lens and any of the Canon EOS line of cameras. When used with a compatible lens, such as the Canon EF 500mm 4L IS USM, they will multiply the focal length of the lens by a...

tele-converters on newer EOS bodies. Auto-focus works only on the 1.4× Extender and image stabilizer(IS) works with both 1.4× and 2× Extenders.