Order one grounding clip for every two top mounting clamps (end clamps + mid clamps) in your installation. Only one of the two rails in each row requires grounding clips.
Note: This product was used with the 1″ wide Unirac mid clamps that did not have integrated grounding. All new Unirac mid clamps have integrated grounding teeth and do not need the UGC-1 grounding clip. These clips are no longer in production.