I bought a 2S robotic window cleaner after advice from an online representative of Robot My Life. It performed poorly leaving streaks and marks on our glass windows and doors. I spoke/texted/emailed the company. They have refused a refund. 1. The 2S would occasionally become fixed in one spot and have to be turned off and manually removed. Luckily, I could reach it each time, otherwise I may have had to wait for it to lose suction and fall off. 2. Their special glass cleaner would not reach the glass if there was even a slight breeze. 3. Dry cleaning of the windows with clean pads each time could possibly have made some difference to cleanliness of the windows but the machine still made unacceptable marks and streaks after doing the wet clean. 4. Sometimes the 2S became wedged under the glass door handle. Again, it need to be turned off, removed and restarted. 5. The 2S occasionally only ascended/descended half the glass, would turn around and clean the part if had already been over. It would need to be stopped and restarted. 6. I cleaned the caterpillar tracks between each window - I noticed no difference in the results of the glass. 7. The 2S needed constant supervision as it often stopped in one spot, became wedged or omitted cleaning part of the window. 8. It is extremely noisy and uncomfortable to be in the same room while it is "working". The company said the streaks and marks were due to an oil build up on my windows. The only way that could happen is if the 2S left oil on my windows. I cannot recommend this machine. All my glass windows and doors need manual cleaning AFTER using the 2S. Manual cleaning was quieter, faster and had a better result - no marks and streaks on the glass.