→Thin cast iron helix oil rings for road vehicles and other reciprocating internal combustion engines with cylinder diameters ranging from 60 mm to 110 mm.GB/T1149.15-2017 specifies the basic dimensional characteristics of thin cast iron helical spring oil rings of piston rings models DSF-C, SSF, GSF, DSF, ssf-l, DSF-NG and DSF-CNP.