Magic’s Adapter Bushings are designed to increase a 1½˝ MBT fitting to a 2˝ MBT fitting simply by threading the adapter to the female threaded fitting. The internal thread of the bushing is 1½˝ FBT with an O-ring (included), ensuring a positive seal. The external thread is 2˝ FBT. You can choose from two configurations, one with O-ring groove for Heater applications and one without 0-ring groove for Pump Union applications. Adapters are manufactured from quality PVC.