I am from germany and I can tell you they are nonames over here. Nobody heard of them actually.
As far as I know, Yarbo brand was "started" by vt4c.com, after plenty of searching all over the web I couldn't find any other reference to Yarbo in the context RCA/banana/spade
They are made out of gold plated brass. For the price you can't expect much more, but they are advertised as being high-end, and they are not(no brass is high-end unless it's in the instruments
), so there lies the stinkin' fish.
I ordered from this guy in the past some bulk silver cable, some RCA connectors and they do sound OK for the money, but it just DOESN'T compare to stuff like VH-Audio's silver wire or some Eichmann Bullet Plugs. They are in a much higher league, but so is the price
Anyway, I don't think I would order again from vt4c.com, at least not connectors/silver wire. In the end, I don't need a lot of RCA connectors, so I'd rather wait get something better than buy something I have no idea what it is, even if it is cheap, sounds decent, is labeled as "Highly recommend"(sc), "Best Price/P"(sc) and "Best SONIC"(sc).