  We develop a microscopic formalism to study the fractional quantum Hall
plateaus at filling factors $\nu $ away from $1/2\beta$ $\beta$ an integer. The
theory is in terms of quasiparticles which carry a charge $e^{\ast}$ equal to
$1-2\beta\nu $ times the charge of the electron. The wave functions obtained
following our approach are shown to coincide precisely with the form predicted
by Jain and this holds independently of the interaction potential.\
Microscopically this rigidity originates from the fact that two different
charges interacting attractively in their lowest Landau levels form a bound
state with a universal wave function. From the expressions of the gaps we
compute an effective mass which agrees well with the experiments carried at
$\nu=1/2$ and 1/4.
