The Kärcher gutter and pipe cleaning set PC 20 is compatible with high-pressure cleaners of classes K 2 to K 7, including the K 7.

Yes it works perfectly I at least am satisfied

Yes, the gutter and pipe cleaning kit fits the K4 Premium. The hose is connected directly to the high-pressure gun instead of the jet pipe.

I have a K3. It has the Kärcher standard connection and fits. If the K4 also has this standard, it will certainly fit. According to other questions/answers, K5 also works. So K4 should not be a problem either.

The connection of the gutter set is the same as on the handle of the Kärcher, simply connect it. I have a 10-year-old K5 that fits.

Yes, of course, a great step forward has been taken.