The constant wear and tear from rough roads and heavy loads can cause a standard shackles to simply wear out. The heavy duty shackle kit is an excellent upgrade for your running gear and the answer for wear and tear. The shackle bracket is a stronger, more durable bracket that is much less subject to having the bracket elongate. The Bronze Bushings and wet bolts provide an opportunity for periodic lubrication that will greatly extend the product life. The heavy duty shackle kit is for tandem axle trailers and will fit units with upgraded suspension systems.