Flair-It 3/8" PEX Tee. It is made of durable Polyoxymethylene material, resistant to stress fractures and extreme temperatures. Easy to install, simply cut the tubing square, slide the nut along the tubing, rock the fitting all the way into the tubing, slide the nut back onto the fitting and tighten it as far as it will go. Compatible with any brand or type of SDR-9 PEX or PE-RT tubing as well as Polybutylene pipe. Use manufacturing part #06790, PB Adapter Sleeve, when using FLAIR-IT fittings with 3/4 inch Polybutylene pipe.