The Claber 91021 is a 1/2-Inch threaded corner connector that connects Colibrì underground Pop-Up micro-sprinklers to the 1/2-Inch main tube /hose pipe. It is made of polypropylene (PP) and is guaranteed to be perfectly watertight. The Claber 91019 is a perfect component for a Pop-Up Sprinkler Irrig..