The hose conversion adapters is required when you upgrades your existing Intex pool filter pump system 1000gph or smaller to any of the more powerful 1500gph or larger pool filter pump. If your pool is 16' in diameter of smaller, you would need this set 2 converters in the set to adapt to the larger 1.5" ID hose with threaded connection to your 1.25" ID hose connection.