 All 481 ships of this type had the same general characteristics.The only significant variation within the type was one of appearance; "YMS-1" through "YMS-134" had two stacks, "YMS-135" through "YMS-445", "YMS-480", and "YMS-481" had one, while "YMS-446" through "YMS-479" had none.Originally rated as service craft, they were used during World War II for inshore sweeping to prepare the way for amphibious assaults.