The sucker-version of the easy cable clip has been put through the same tests as its tubed cousin, the 'cable clip from tubing'. For an overview of the variety of cables tested see http://www.instructables.com/id/Cable-clip-from-tubing/step7/Testing-the-cable-clip
The case of a mobile phone charger with a mass of 180 g (0.40 lb) is delicate: firstly because the continuous force on the suction cup might loosen it over time, and secondly because the transformer easily bumps against the glass (when stuck to a window) which involves a risk. Therefore, preferably use the sucker version clip with light material, such as connector cables. An overview of alternative objects for using the sucker clip with is provided in the next step.