Gravel is sized to model gravel roads more realistically. Use Accent for shoulders and to model bare spots on roads. Gravel Gray Coarse. Gravel- 10.8 in3 (176 cm3). Accent Powder- 1.8 in3 (29.4 cm3). Coverage: Models a gravel road 12' x 2" (3.65 m x 5.08 cm)