Made of natural rubber Resistant to boiling water 100% leak proof Keep you warm in winter Detailed ... as copperVol / size300ml – 2000mlFeature1, First grade natural rubber hot water bottle,2, Resistant to boiling water; 3, 100% leak proof4, Seamless moldedRubber content28 ... 100%pressure leak detection test.The hot water bag is made of by Natural Rubber material, also can with kinds of cover ...