The Courtyard 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 Courtyard Floors Pack comes with these 28 pieces:
(4) 4x4 Flagstone Floor
(4) 1x6 Flagstone Floor
(8) 1x2 Flagstone Floor
(8) 1x1 Flagstone Floor
(2) 2x2 Flagstone Floor w/ Small Trapdoor
(2) Small Lattice Trapdoor