This is a Spread 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 12,300 icons, all in the same style and quality.
Consider a circle to which an arrow mark is attached. There will be two circles separated by some distance to for which one arrow is towards the north-east direction and other is towards exactly opposite to it on the adjacent circle pointing towards south west direction. These two circles lie on an imaginary line which is at 45 degrees to the horizontal.