This replacement bolt on front spring hanger for boat trailers is made out of hot dipped galvanized steel. This simply bolts to the frame of your trailer using 3/8 inch bolts. This spring hanger is used on 1 ¾ inch wide slipper spring. The bolt to attach the slipper spring to this hanger would be a ½ inch. This Spring Hanger is most commonly used on Light Duty Trailers when mounting a Slipper Leaf Spring. This is the Front (towards the front of the trailer) hanger. If you need the Rear also, select Boat Trailer 2 Hole Bolt On Rear Spring hanger to complete one side of your Slipper Spring set-up. If you are needing 3/8 inch Mounting Bolts, go to Boat Trailer Bolts.