... 3.short delievery time. 4.better service COD pipe and machine 1)corrugated/spiral shape 2)co-extrusion forming 3)3 ... squeezes out becomes. It bears the high pressure, but is curving, has the discriminati on, the easy construction is the main ... 2 2 1Test itemTechnical RequirementTest Resulttest dataconclusion1. Outshapeinner/outer wall smooth, color evenly, no bubble, no cracks, no impurity,no ...