Very cheap, but good.

I tried the set and was satisfied. Cleaning performance very satisfactory. I first wanted to buy a higher-priced Lenspen, but I see no reason. The pen is replaced anyway from each 0.5-1 years.

The mentioned dyeing of paper in my opinion is normal. The graphite powder in the felt is used as a cleaning agent for heavier stains. I have not tested this Pen on the lens, but observed already friends with high end Lenspens the same effect. There, the lens was by paint, blow and finally clean the final cloth cleaning.