These baluns and ununs can be used for impedance matching and also as End Fed halfwave antenna matching transformers to 50 or 75 ohm coax cable.
Ferrite Snap On, ID = .514in/13.1 mm, 10 Pack for troubleshooting unknown RFi frequencies
Use Mix 31 for 1-300 MHz - 4 pieces
Use Mix 61 for 200- 2000 MHz - 3 pieces
Use Mix 75 for150 KHz-10 MHz - 3 pieces
At last a troubleshooter's ferrite kit that works from 150 KHz to 2 H=GHZ. Now you can suppress RFi from unknown frequency ranges with a full spectrum of ferrite cores that have a 1/2" ID large enough for multiple turns of many common data and signal wires. Try 1 mix and see if it has an effect and if not then try another until you suppress the unknown frequencies. Or use them all to provide protection across a broad frequency range. 3 ferrite cores provide at least 500 ohms in the frequency band to give a measurable difference in RFI and noise suppression.
Square or Hex sided depending upon inventory stock