Prevue Pet Products Nature's Hideaway Grass Balls are a hand-woven grass activity center for your small animal. The sweet fragrance of 100% all natural grass materials comes through in this fun playtime accessory while satisfying your pet’s natural instinct to burrow, explore and nest. Our Medium Grass Ball measures approximately 7” in Diameter, ideal for a hamster or guinea pig. Our Large Grass Ball measures approximately 9” in Diameter, ideal for a guinea pig or ferret.