  We review the experimental limits on mass of excited fundamental particles
and contact interaction energy scale parameters $\Lambda$ for QCD, QED and
electroweak reactions. In particular we have focused on the QED reaction $
\EEGG $ at the energies from 91GeV{} to 202GeV{} using the differential
cross-sections measured by the L3 Collaboration from 1991 to 1999. A global fit
leads to lower limits at $ 95 % $ CL on $\Lambda > 1687$ GeV, which restricts
the characteristic QED size of the interaction region to $ R_{e} < 1.17 \times
10^{-17} $ cm. All the interaction regions are found to be smaller than the
Compton wavelength of the fundamental particles. This constraint is used to
estimate a lower limit on the size of a fundamental particle related to
gravitational interaction, applying the model of self-gravitating particle-like
structure with the de Sitter vacuum core. It gives $r_{\tau} \geq 2.3 \times
{10^{-17}}$ cm and $r_{e} \geq 1.5 \times 10^{-18} $ cm, if leptons get masses
at the electroweak scale, and $r_{\tau} \geq 3.3 \times {10^{-27}}$ cm, $r_{e}
\geq 4.9 \times 10^{-26} $ cm, as the most stringent limits required by
causality arguments. This sets also an upper limit on the gravitational mass of
a scalar $m_{scalar} \leq{154} $ GeV{} at the electroweak scale and (m_{scalar}
\leq \sqrt{3/8} m_{Pl}) as the most stringent limit.
