Material and surface:
Type RK-AL of aluminium AlMgSi 0,5; fine lathed, in natural colour or anodized black.
Type RK-ES of stainless steel 1.4305; fine lathed.
Type RK-PA of polyamide PA6, glass ball reinforced in black similar to RAL 9005 or grey white similar to RAL 9002, half-matt with fine structure.