  The high-precision HERA data allows searches up to TeV scales for Beyond the
Standard Model contributions to electron-quark scattering. Combined
measurements of the inclusive deep inelastic cross sections in neutral and
charged current $ep$ scattering corresponding to a luminosity of around 1
fb$^{-1}$ have been used in this analysis. A new approach to the beyond the
Standard Model analysis of the inclusive $ep$ data is presented; simultaneous
fits of parton distribution functions together with contributions of "new
physics" processes were performed. Results are presented considering a finite
radius of quarks within the quark form-factor model. The resulting 95% C.L.
upper limit on the effective quark radius is $0.43\cdot 10^{-16}$ cm.
