AF-480 is a single-acting wiper and AF-485 and AF-487 are double-acting wipers. The two kinds have slightly different geometry with wiper lips that are installed back-to-back in one seal. The wiper utilizes an O-Ring as an energizing element.
The O-Ring maintains the pressure of the wiper lips against the sliding surface when system pressure is absent. The wipers serve to clean away contaminants from the retracting rod, and prevents the system from getting soiled, while leaving a residual oil film on the extending rod on the pressurized side.