For your 1999 Mercury Mystique, I would recommend the Curt Class I Receiver, part # C11113. The installation hardware is included with the receiver. I will provide a link below to the installation instructions. You will also need a Draw Bar # C45016.
You will need the appropriate trailer ball, if you do not already have one. The coupler on your trailer should have the necessary ball size stamped on it, which should be either 1-7/8 or 2 inch.
For a 1-7/8 inch ball I would recommend part... view full answer...