The best way to determine which set of rails you will need is by finding the model number of your table.
You can find it by taking the Ball View Door off the side of your table.
Stamped on the inside of the table is the model number
The 7 ft. tables have 3 different style rails, use the table below to determine what style you have, if you have a ZD-7, follow the guide here to find out if you have the newer or older style
Here is a link to our guide on what to measure for the 7ft. ZD-7 tables.