This Jeden do jednego icon is made in Material Design style developed by Google. This style is based on extremely simplified shapes, thin two-pixel lines, and is optimized for 24x24 px. Unlike other vector icon packs that have merely hundreds of icons, this icon pack contains 4,300 icons, all in the same style and quality.
The image is a square. The top and bottom are a little bit longer than the sides of the square. The square has the number 1, a colon, and another 1 in the center. The numbers are not touching the edge of the circle.