This is a really useful minor third based lick, straight out of the pentatonic minor scale. Though come to think of it, we're using one note from the next box pattern as well.
Here's the tab for the lick:
The minor third is created by those first two notes in the riff. The lower note is an E, and the second one is a G.
If you're looking for ways to get some more mileage out of this riff, try sliding into both of those notes together, playing them as a double stop. Because that interval sounds so great, there's a lot that can be done with it rhythmically.
Don't be shy, give it a try over a jam track!