Sandwich rubber is a single layer of cellular rubber covered with a single outer layer of ordinary pimpled rubber, the thickness of the pimpled rubber not benig more than 2 mm .

• “普通颗粒胶”是一层无泡沫的天然橡胶或合成橡胶，其颗粒必须以每平方厘米不少于10颗，不多于50颗的平均密度分布整个表面。