The 8x8 Flagstone Floors Pack is part of the Castle Builder System. It is made of "Dwarvenite". This item was initially available as an add-on to a pledge level during the Castle Builder System Kickstarter. The item comes in both painted and unpainted versions.
The 8x8 Flagstone Floors Pack comes with these 2 pieces:
(2) 8x8 Flagstone Floors