All choke coils in this series are Durez covered and EIA color coded. They have an inductance of +/- 10% and leads are No. 20 AWG tinned copper 1-1/2" long. Parts U150 through U501 are wound on 0.156" dia. phenolic forms with body length dimensions 7/16". Parts U601 through U102 are wound on the same form with body length dimensions 1/2". Parts U252 through U752 use 0.156" dia powered iron forms, with body length dimensions 7/16". Parts U103 through U503 use 0.187" dia. iron forms, with body length dimens ions 5/8". Diameters of coils vary from 1/4" to 5/8" depending on inductance value.