This is a Collage Filled icon. We've made it in iOS style, first introduced in iOS version 7 and supported in all later releases up until now (at least iOS 11). This style is based on thin two-pixel lines and is optimized for 50x50 px. Unlike other vector icon packs that have merely hundreds of icons, this icon pack contains 12,800 icons, all in the same style and quality.
The icon is a square composed of four separate sized rectangular tiles, arranged in such a way that each horizontal half resembles a one hundred eighty degree rotation of the other. The tiles on each side are asymmetrical in terms of their size.