This screw do counts, Profile, rectangular wire, tubing, and granulation. Screw compression ratio can be based on different products and different formulas for design. Product Description: Top quality alloy steel 1)38 CrMoA1A(JIS SACM645)2) 9 Cr18MoV Surface treament: Tungsten Carbide Paint anti wearing and corrosion double metal layer Technical Parameter: Deepness of Nitriding Layer 0.50-0.80mm Hardness of Nitriding: 900-1000HV Nitriding Brittleness: First Class Surface Roughness: Ra0.4 Screw Alignment: 0.015mm Hardness of Chrome Plating Coating after Nitrding above 950Hv Thickness of Chrome Plating Coating: 0.025-0.085mm