A device for contactless measurement of a particle state variable of a flowing medium that contains electrically charged particles is disclosed, in which a sheet-like sensor element is disposed parallel to the particle flight direction, or at least two sensor elements, such as electrodes, are disposed in succession in the flow direction. The paint brush holder when attached to the rim of a paint container, allows the user to rest the paint brush in the paint brush holder and allows the principle of inertia of the paint brush, acting on two points to create a grip on the paint brush handle. The server system sends a data collection command to at least one second client device of the plurality of client devices in accordance with the characteristic criteria. , Co2; a compound, or salt of magnesium, e. A thickness of each of the second heat sinks is gradually varied along a height direction of the each of the second heat sinks. Either the secondary back or a separate polishing substrate adhered to the secondary back also forms a polishing or non-abrasive cleaning surface.