Secondary Sets also known has Piggyback sets. These sets are used in conjunction with Primary Sets, usually connecting to a Y-Site on the Primary line. When a secondary set is used the primary set should contain a back-check valve, which prevents the retrograde flow of fluid from the secondary container into the primary container. Secondary Sets are usually between 18- 70" long, but the most commonly used length is 30-36". Secondary Sets can be Macrodrop or Microdrop depending on the volume and rate of the secondary solution and the patient's condition.