This replacement bolt on 4 hole front spring hanger for boat trailers is made out of hot dipped galvanized steel. This hanger can be used as a front hanger on a single axle trailer. Also it can be used as the front and rear hanger on a tandem axle trailer. It simply bolts to the frame of your trailer using 3/8" Trailer Bolts. This spring hanger is used on 1 3/4" wide Double Eye spring. The bolts to attach the double eye spring to this hanger would be a 9/16" Leaf Spring Mounting Bolts. This 4 Hole hanger will mostly be mounting to a boat trailer with an Aluminum I-Beam Frame. The spacing of the mounting holes is design to allow the bolts to mount on either side of the beam.