I had previously ordered a line isolator or a 1:1 balun from ArraySolutions in the belief that it was the best available.
I learned that Balun Designs LLC were making a similar item with even greater isolation.

An inquiry to ArraySolutions by email asking them to provide me with test data on the isolation impedance of the choke resulted in no reply.

I am disappointed by this, I expected more from ArraySolutions.

The same question posed to Balun Designs resulted in an answer within minutes – On 160 meters the choking impedance is 1536 ohms at 1.8 MHz.

I purchased the Max choking model along with a 1:2 UNUN (25 to 50 ohms) both of which are obviously of high quality.

I have since learned that the impedance of the King´s antenna will be close to 15 ohms, so I should have ordered the 1:4 UNUN but not to worry, I will be building other antennas later and will find a use for it.