Thank you for your question about the Delta 16" shower arm and the Delta Ceiling Mount Shower Arm & Flange and I'll be happy to assist you with this today.
Unfortunately, you will not be able to connect those two shower arms together and I apologize for any inconvenience this may cause.
If you are interested we do carry an extendable shower arm that reaches between 13-22 inches, Model #U6930-RB.
I hope this information is helpful.
Delta Faucet Company
Date published: 2018-03-02