These unique heim center finders are designed to allow the racer to set up spare arms once the car is set up. This is done simply by remving the arm, bolting the tape measure center finder into one end and placing the center pointer on the other and measuring When you establish a measurement place the finder set into the spare and adjust to match the length of the heim. When the tape end is bolted in, snug it, hook it, and pull it to let the finder square itself. then just tighten, and you are ready to go. We designed this product to take the work out of eyeing up bolts in a critical situation when an identical spare is crucial. Finder sets are available for 1/2'', 5/8'', and 3/4''. This is our 3/4'' set.