A Roots-type supercharger uses paddles on two rotating drums to push air into the intake.[2] Because it is a positive displacement device, this compressor has the advantage of producing the same pressure ratio at any engine speed. A screw-type supercharger is also a positive displacement device, like a Roots-type supercharger. Screw-type superchargers are more complex to manufacture than Roots-type superchargers, but are more efficient to operate, producing cooler air output.