Mark: FK (Interior)

GOST 3916.1-2018
Standard sizes, mm (ft): 1525х1525
Standard thickness, mm: 3 - 40
Grading: I/II (B/BB), II/II (BB/BB), II/III (BB/CP), II/IV (BB/C), III/III (CP/CP), III/IV (CP/C), IV/IV (C/C)

Mark: FK (Interior)

GOST 3916.1-2018
Standard sizes, mm (ft): 1525*3050
Standard thickness, mm: 9 - 40
Grading: III/III (CP/CP), III/IV (CP/C), IV/IV (C/C)

Mark: FSF (Exterior)

GOST 3916.1-2018
Standard sizes, mm (ft): 1525х1525
Standard thickness, mm: 6-21
Grading: II/IV (BB/C), III/III (CP/CP), III/IV (CP/C), IV/IV (C/C)

Mark: PF-A FK

GOST 8673-2018
Standard sizes, mm (ft): 1525*3050
Standard thickness, mm: 9-40
Grading: II/III, II/IV, III/III, III/IV, IV/IV