Simplex piston air compressors are the most common industrial air compressors available, using displacement principles to increase the pressure of enclosed air. Piston compressors typically benefit the consumer by carrying lower prices, less maintenance, and boasting a high availability of spare parts. Pressure lubrication for air compressors usually comes in a pair of designs — pressure lubricated and splash lubricated. The prior have a crankshaft-driven pump to get oil to critical components within the compressor. Splash lubricated air compressors have a "dipper" at the bottom of a piston connecting rod that splashes oil inside of the case.