Gniazdko and other 85,000 icons from Icons8 icon pack follow the visual guidelines of the operating systems: Windows, iOS, Android KitKat, and Material. PNG format is free up to 100x100 px. Icons are availble for download in PNG and vector (SVG, PDF, EPS, and more).
The icon is shaped like a square with curved corners. Inside of it is a circle that takes up half of the square. Inside the circle are two dots, one at the left center and the other towards the right center.