The Pentair 27001-0022 is a tapered threaded fitting that can be fit into a plastic drain pipe to close or seal the opening.

 
Replacement for the following:
• Pentair Sta-Rite PLM, System 2 and 3 modular media cartridge filter models S7M120, S7M400, S8M150, S8M500, PLM100, PLM125, PLM150, PLM175, PLM200, PLM300
• Pentair Sta-Rite PLD, System 2 and 3 modular media pool/spa D.E. filter models PLD50-DE, PLD70-DE, PLDE36-DE, PLDE48-DE, PLDE70-DE, S7D75, S8D110 • Sta-Rite System 3 S7S50, S8S70

Specifications:
• Part number: 27001-0022
• Dimensions: 2-1/2”x1-1/4”x2-1/8”