Mundorf BS140 coils are high performance models for low frequency filtering. The core is made of Feron which is heat treated after production. This treatment gives it an optimal internal structure for good magnetic characteristics with very low losses and low distortion. Their power handling is also higher than conventional ferrite core coils. The "Baked Varnish" finish of the BS71, BS100 and BS140 series allows to limit vibrations and to use a maximum wire diameter for a reduced electrical resistance.