Ruffwear Gnawt-A-Rock - It looks like a piece of Obsidian from our nearby lava flows, but it's Gnawt-A-Rock This durable throw toy is inspired by natural volcanic glass formed by rapidly cooling lava from Pacific Northwest volcanoes. Unlike Obsidian, the Gnawt-A-Rock is made with natural latex rubber, with a faceted, gum-massaging surface. Its irregular shape creates an erratic bounce, and it has a treat-dispensing design for interactive play and reward. Internal chamber dispenses kibble or small training treats Made from natural rubber, a renewable, sustainable resource Durable, chew-resistant Erratic bounce for engaging fetch Faceted surface for gum-massaging Size suitable for large-mouthed dogs