What do you guys make of this vent connection at the chimney?

What do you guys make of this vent connection at the chimney?

Not allowed here Local AHJ rules no flex.
Looks like it might be a Z-Flex liner:


That looks like it. Thanks. I told my client you guys would get back to me quick!![]()
You might wan to check that .PDF - I know you need a listed connnctor if to B-Vent, I don’t know about single wall, though.