These trailing arms are designed to bolt on in place of the stock units, allowing adjustability of the driveshaft and positively controlling fore and aft movement of the rear axle assembly.
For cars a stock ride height, simply remove the old trailing arms, adjust the length to equal that of the originals. Note- washers will be required to make up the mounting width.
For lowered cars, adjust the arms to attain the straightest possible driveshaft angle with the car at its normal ride height. Occasional lubrication of the rod ends is recommended to reduce squeaking and to prolong the life of the rod ends.