Students engage in labor practice at a factory using 3D printing technology to create models. As shown in the figure, the model is a rectangular prism $ABCD - A _ { 1 } B _ { 1 } C _ { 1 } D _ { 1 }$ with a square pyramid $O - EFGH$ removed, where $O$ is the center of the rectangular prism, and $E , F , G , H$ are the midpoints of the respective edges. $AB = BC = 6 \mathrm{~cm} , AA _ { 1 } = 4 \mathrm{~cm}$. The density of the 3D printing material is $0.9 \mathrm{~g} / \mathrm{cm} ^ { 3 }$. Disregarding printing losses, the mass of material needed to create this model is \_\_\_\_\_\_.
Students engage in labor practice at a factory using 3D printing technology to create models. As shown in the figure, the model is a rectangular prism $ABCD - A _ { 1 } B _ { 1 } C _ { 1 } D _ { 1 }$ with a square pyramid $O - EFGH$ removed, where $O$ is the center of the rectangular prism, and $E , F , G , H$ are the midpoints of the respective edges. $AB = BC = 6 \mathrm{~cm} , AA _ { 1 } = 4 \mathrm{~cm}$. The density of the 3D printing material is $0.9 \mathrm{~g} / \mathrm{cm} ^ { 3 }$. Disregarding printing losses, the mass of material needed to create this model is \_\_\_\_\_\_.