power transformer, CSA, CQC, UL,VDE, ROHS complaint, Inner Diameter: 17.8mm,outer diameter:21.4mm,sample first toroidal power transformerCircumstance temp 0--+40 degreeAppearance &dimension: as imageInner Diameter: 17.8mmOuter diameter:21.4mmDC resistance: at 25 degree 2.5Ω ± 10%If needed, techonical drawings can be provided.