This is a Additional 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 very simply composed of an empty circle with a large, upper case letter A in the center, about as wide as the circle's radius. The icon stands for the presence of additional elements outside of the ones currently being represented on the screen.
Related to Additional Icon
Related icons are the icons with matching tags, as well as all ecommerce icons. All icons are in the same flat style. You can either download free PNG icons or buy SVG vectors