knob: light metal unpolished or polished(+) aluminum, grey cast iron GG 20, bright; Stainless steel A2, dull blasted; Stainless steel A4, polished;
hole: female threaded blind hole.
Characteristics:
type 2: the stainless steel A4 version ensures maximum corrosion resistance, with a smooth finish, so convenient for all applications having high hygienic requirements (e.g. food industry);
