This is a 4k 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 12,900 icons, all in the same style and quality.
This is a square, with the top and bottom lined with several smaller squares. The characters "4K" are in the middle of the big square. There are eight squares that align both the top and bottom of the big square.