Canon/Sigma 1.4x or 2x converters

[Combat squirrel]

Basically looking at the titled converters, but do these only work with EF lenses ? do any work with EFS lenses ?

 

[olv]

What EF-S lenses were you planning on using with it? I don't think many of the EF-S lenses actually have a fast enough maximum aperture for it to be worth it even if they did fit.