The correct cords for the FT-253 are 2 each CD-280. CD-280 consists of either 15'-0" or 15'-6" (depending upon where you look) of #6 AWG single conductor shielded cable. Rubber jacketed and rubber insulated. The shield is light duty and is not intended for current carrying but only as an electrostatic shield. Which is why two were used. The stranding of the #6 wasn't given other than by reference to a GE number but it is quite flexible.