Barrels and screws are listed as injection-machine spare parts in standard, PVC and bimetallic types. The standard barrel uses 8550 (38CrMoAl) nitriding steel, 96-hour gas nitriding, surface hardness 58–62 HRC and a nitrided depth of 0.5–0.8 mm. The ring, check ring and washer use 2379 (SKD11 – X155CrVMo12) cold-work tool steel, vacuum hardening to 62–64 HRC and a tungsten-carbide coating. The PVC screw uses 4140 (42CrMo4) quenched-and-tempered steel with hard chrome 0.05–0.08 mm thick at 62–65 HRC. The bimetallic barrel adds a centrifugally cast bimetallic alloy on 8550 steel, with hardness 62–72 HRC, an average of 68 HRC and an alloy thickness of 2.5–4 mm.