PQ Series Ferrite Cores with Low Loss and High Frequency, Made of Mn-Zn Soft, Used for Transformer Materials: Mn-Zn, NH2B and NH2C grade (equivalent to TDK PC40 and PC44) Series: PQ2016, PQ2020, PQ2620, PQ2720 and PQ5050 Available in various sizes Used for transformer PQ Ferrite Core