FlexiGas 28mm x 22mm Copper Connector (for connect CSST to copper tube) Flexigas™ patented fittings create a 100% metal-to-metal seal (with no plastic gaskets or o-rings). As the fitting is tightened, the last corrugation of Flexigas™ CSST tubing is deformed into a flared configuration against the metal seat of the fitting. The sizable and reversible collets are easy to handle and align the Flexigas™ tubing assembly with the fitting during installation.