Sigma APO Teleconverter 1.4x EX for Select Sigma Lenses for the Canon EF-MountCosmetic Condition: Please note: This teleconverter is compatible with some telephoto Sigma EX series lenses primarily sold in the early 2000's. This will not work on newer lenses from Sigma. Please check the compatibility with your lens before purchasing this, as it only works with a handful of lenses. Includes: Front and rear caps. S N: #2004838