1.over 18years experience for screw and barrel 2.alloy-steel of ... brittleness: ≤ 2grade7.Surface roughness: Ra0.4μm8. Screw straightness: 0.015mm9. Max.length:≤10000mmMaterial of barrel inside ... of screw barrel to meet customer's demand. Gradual type,mutant type,wave type,barrier type,double screen ... type,exhaust type, pin type, mixed type, double-head type,three-head type,multi head type etc ...