The Alleys Set is part of the City Builder System. The Alleys Set is made of "Dwarvenite". The Alleys Set was initially available as Add-On item during the City Builder System Kickstarter. The item comes in both painted and unpainted versions.
The Alleys Set comes with these 10 pieces:
(2) Alley, Curve, 4x4
(4) Alley, Street Intersection, 4x4
(4) Alley, Straight, 4x4