Includes rubber duck bill and black plastic insert.  This replacement duck bill can be used to rebuild the following:

• CSI Reactr/Hydroxr air intake check valve (65555X250)
• WaterSoft  Centuri air intake check valve (20944C250)
  
• Old-style CSI Nitro/Nitro Pro air injector (20009X007)*
• Old-style CSI Sidekick air injector **
• Old-style WaterSoft Sidewindr air injector** 

*The old p/n 20009X007 can be replaced by the new-style 20017X012

**The old side-mount air injector assy can be upgraded to the new style air injector assy 20017X010