Ferrules, for use with Two Piece, High Pressure, Tubing Connectors for 1/16th PEEK Tubing. Universal Double Cone. ARE-Applied Research brand. This Double Cone Ferrules will swage on to the PEEK tubing in two places for a great grip on the tubing. Also, when the MicroSolv Brand 2 Piece PEEK Tubing Connector is used, the shape of this ferrule will not twist the tubing when you turn the fittings.