Piston Seals maintain sealing contact in sliding motion between the piston and the cylinder bore. Differential pressures acting on the piston to extend or retract the piston rod.  The pressure acting on the Piston Seal increases contact forces between the Piston Seal and cylinder surface. Therefore, the surface properties of the sealing surfaces are critical to proper seal performance. 
DPV
Polyurethane slide ring, nitrile rubber energizer; fits wide, shallow inch size housings; suitable for heavy duty applications.
CPV
Polyurethane slide ring, nitrile rubber energizer; fits wide, shallow inch size housings; suitable for light to medium duty applications.
PTB
PTB Polyurethane U-cup profile with incorporated nitrile rubber X-ring, which provides good performance even at low pressure and temperature.
STD
STD Polyurethane U-cup profile with incorporated nitrile rubber X-ring, which provides good performance even at low pressure and temperature; narrow housings.
GH
GH PTFE slide ring, nitrile rubber energizer; low breakaway friction.
UNP
UNP Polyurethane U-cup profile; single-acting; may be used in double-acting cylinders when facing in opposite directions.
LTP
Sealing ring made of nitrile rubber, supported by polyamide anti-extrusion rings; good gap extrusion resistance; suitable for high pressures.
DZ
DZ Nitrile rubber primary sealing ring, polyurethane secondary sealing ring; low friction; suitable for heavy duty applications.