Guren is made of precise carbon steel & process  the HV500 Coat for the surface.
This plating reinforced a hardness of the surface so achieve around HV500.
It’s better than stainless steel (from HV200 to 400)
It’ll be kept clean & beauty surface for long time.
Of course, it’s good for anti rust.

Guren 1 is simple design.
The muzzle end has crown cut.
Low cost barrel series but its potential is enough for upgrading.

da Vinci GUREN 1 6.03mm Carbon Steel Inner Barrel for Marui G18C AEP (110mm)
Metal Construction
High grade precision barrel at 6.03mm diameter for extra power and precision shooting
Suitable For Tokyo Marui G18C Series AEP Airsoft Guns
For custom upgrade user, you can choose a longer barrel
Dia.: 6.03mm
Outer Dia.: 8.55mm