The RU-1:1 is a 1:1 Unun intended to help remove unwanted RF from the coax cable shield. 

It is normally used as a common-mode RF choke for short coax cable runs or non-resonant antennas.

The RU-1:1 features SO-239 sockets for both input and output.

• Configuration: 1:1 Unun
• Frequency Coverage: 1.8 to 30 MHz.
• Power Range: to 200 watts PEP
• Easy to weatherproof
• Enclosure size: 5 x 2.5 x 1.25 (measured in inches)
• Weight: 6 oz (with enclosure)