Generally the performance of centrifuge are specified in func tion of the maximum achievable speed. However the speed represents only approximately the real force developed into the sample that generatesthe separation.This force is expressed like relative centrifugation force (RCF).Its value indicates how many times the centrifugation force exceeds the natural gravity acceleration "g”.Observing the lateral formula it is clear that RCF is directly pro portional to the axis of rotor and linked to the square of speed.It means that, for example doubling radius, RCF doubles and it quadruples with doubling of speed.As a consequence the performance of centrifuges should be compared only on RCF values.