Repairing WC -Vertical outflow

[gnvqsos]

I have a ground floor WC where the waste flows out vertically via a solid concrete floor.The e3xisting vertical connector was secured by a collar of sand and cement.The connector goes directly into the void.
Can I use a new connect similar to the existing one or is it better to fit an adaptor into the remains of the cast iron pipe and then fit the vertical fitting into the adaptor?

 

[CBW]

If it’s a concrete floor, I doubt it’s cast iron. Probably salt glazed pipe. If you’re replacing it, could go like for like, or a dc1-by connector.