Horse Trailer Breast or Butt Bar, AluminumHorse Trailer Breast or Butt Bar, Aluminum This butt or breast bar is meant to replace old or broken bars, straps or chains on a straight load or side by side horse trailer. The bar is made from 1 3 4" outer diameter aluminum pipe. It has closed welded ends, with a attached steel ring at each end. The bars are measured by the length of the bar only, not counting the rings. We recommend that you order a bar 8" less than the width of the trailer stall,