Ferrite ring by Micrometals, part number T37-7. Colour is white with black on one side. Constructed from no. 7 material.
Used in RF circuits from 1-25MHz. Dimensions
Outer diameter - 0.375"/ 9.53mm
Inner diameter - 0.205"/ 5.21mm
Thickness - 0.128"/ 3.25mm Available as 2, 5 or 10pc pack size.