The RS stands for Rapid Speed because the velocity is much higher than with the regular pellets. Also the ballistic curve will be very flat. There is also a connection with a car industry where RS is nickname to their sport models (Rally Sport) which are lighter and more powerful than the regular ones. Ideal ammunition for 16J air rifles in cal .22. Muzzle velocity is 192 m/s if the power of airgun is set to 16J.