Are teleconverters generic?

I read somewhere about the existence of generic teleconverters. But how can teleconverters fit all lenses, don't different lenses have different mounts? Sony, Nikon, Canon, etc…

both for the lens element, and the mount to the body.

By generic, they are referring to brands like Kenko, not the mounts. Kenko is one company that makes inexpensive teleconverters for most mounts, at a fraction of the cost of the name brand. A Kenko 1.4x for Nikon, for example, runs about $100 or $150 depending on which model. The Nikon version is almost $400 if I remember correctly, or something close to it.

The same holds true for the other major brands… Teleconverters are not cheap. So the "generic" brands allow you to obtain a TC without the expense of the name brand.

There may be converters that just HOLD the lens…

but you have no guarantees that they are any good…

pay a little more and get dedicated teleconverter…