Designed to fasten luminaires to a tube or pipe withan outside diameter 1-1/2" to 2-1/2” (35mm-65mm). This iron casting clamp is durable to hold a payload up to 220lbs (100kgs). Comes with 3-1/2”steel long shaft and 1/2"-13 bolt & washer. Main body has a bonding position to safety wire to anchor. Note: When using c-clamps care must be taken to not over-tighten the pipe bolt which affixes the clamp to the batten. If this bolt is over-tightened, it can easily dimple or “drill” into the batten, seriously compromising the strength of the batten. A finger tight plus half turn with the wrench is all that is required