Sigma Electric 49004 Beam Clamp, 1-Pack Go to amazon.com Related posts 10 best beam clamp for 2022 FeatureMalleable Iron ConstructionZinc Plated1/4-20 Hole Size; 13/16" Jaw OpeningThis product is UL ListedThis Product is CSA listed Description1/4-20 Beam Clamp from Sigma Electric. Sigma has been a trusted manufacturer of metal conduit fittings and weatherproof products for over 25 years.