2PCS Heavy Duty Trolleys -Product Name:4 Wheel Trolley Assembly -Material:Steel,Galvanized Zinc,rust protection -Max Load rating: 440pound/200kg -Strut rail size:1 3/4 " W. x 2 1/4" H. or Taller -Screw Diameter:M12 (0.47inch/12mm) -Screw Length:4.7inch (120 mm) -Fixed mode:welding positioning or Bolt positioning Usually used to suspend from strut channel with the stud pointing down to support suspended loads,Not recommend to used "upside down" (the bolt side be pointing up). If you are not satisfied after receiving the product,please contact us as soon as possible,we will be more than happy to assist you in this matter.