Carbon-graphite piston rings, used in conjunction with carbon-graphite guide rings or carrier rings that hold piston centered on cylinder bore, are self-lubricating and seal high-pressure gas in applications requiring compressed gases that do not contain oil or grease. Guide rings can be either solid rings or segmented rings with butt joints. At least two rings with off-set segment joints are needed to seal to pressures of 100 psi. Extra sets of rings are required to seal higher pressures.