C Band Feed Rx Circular / Linear Single The CP-300 Pro-Line feed is a single polarity feed. The WR-229 flange is part of a round to rectangular O.M.T. transition that can be rotated to achieve the desired circular polarization. This is helpful at the time of installation making fine tuning adjustments easy and accurate. The CP-300 has the same outstanding “TI” rejection that all A.D.L.Ò Dual Mode feeds have.