This product is made of caoutchouc and it has the better flexibility and durable. A t the same time, it is welcomed both in domestic market and European market. We can manufacture various types of this product, like 2.50-4\2.80-4\3.50-4\3.00-4\4.00-4\3.50-6\3.50-8\4.00-6\4.00-8\4.50-8. If you are interested in any types, please contact us as soon as possible.