... 2)spiral shape 3)3-9 inner ducts 4)varies color COD color pipe C.O.D Corrugated Optic Duct It uses ... 1 Test itemTechnical RequirementTest Resulttest dataconclusion1. Outshapeinner/outer wall smooth, color evenly, no bubble, no cracks, no impurity,no decomposition linepassgrade2 ... testtemp 0°C,height 1m, 1kg hammper impact 10 times, above 9 times no brokenpassgrade7.low tem. Fall downlow temp.-30°C ...