... Belt Structure: Four Parts: Top cover rubber,bottom cover rubber, Reinforced core,Cross rigid.Thickness of top ... Thickness of bottom cover rubber: 1.5-4.5 (mm).Belt core: Nylon,EP,cotton or steel cord ... Base Belt Structure: Four Parts: Top cover rubber,bottom cover rubber, Reinforced core,Cross rigid.Thickness of top ... Thickness of bottom cover rubber: 1.5-4.5 (mm).Belt core: Nylon,EP,cotton or steel cord ...