Our Plastic Case Blocks are an ideal way to indicate Holds or Forwards, as well as reduce errors for routers, swingmen, or unfamiliar mail sorters. The blocks are used like spring clips, but block mail from going into the slots. 9" blocks come 500 per case at 26 lbs. and 11" blocks come 250 per case at 18 lbs. Rural blocks come 300 per case at 26 lbs.