New Tub Drain

HI , new to the forum, great site. I have just replaced my shower stall with a new tub. The old drain was 2 inch copper from main drain reduced down to fit the old shower drain at the trap soldered all the way back.
My question is how do I connect the new tub drain to the old waste line which is 2 inch. do I use the slip fittings, 1.5inch, 2 inch, copper or pvc with the rubber coupler.
thanks for the help
doug

You can use fernco's 1 1/2" x 2" will work fine.