We used archival ROSAT observations to investigate the X-ray surface brightness profiles of a sample of 26 clusters in the redshift range 0.04 < z < 0.06 .
For 15 of these clusters accurate temperatures ( k T _ { X } > 3.5 keV ) were available from the literature .
The scaled emission measure profiles look remarkably similar above \sim 0.2 times the virial radius ( r _ { VT 200 } ) .
On the other hand a large scatter is observed in the cluster core properties .
We fitted a \beta –model ( with and without excising the central part ) to all the ROSAT profiles to quantify the structural variations in the cluster population , unraveling a robust quadratic correlation between the core radius and the slope parameter \beta .
We quantified the shape of each gas density profile by the variation with radius of the logarithmic slope , \alpha _ { n } .
The bi-weight dispersion of \alpha _ { n } among the clusters is less than 20 \% for any given scaled radii above x = 0.2 .
There is a clear minimum spread at x = 0.3 , which is related to the existence of a correlation between core radius and \beta .
These ensemble properties are insensitive to the exact treatment of a possible central excess when fitting the profiles .
On the other hand the scatter is decreased when the radii are scaled to r _ { VT 200 } .

The regularity we found in the gas profiles at x > 0.2 supports the existence of an universal underlying dark matter profile , as already predicted by theoretical works .
It suggests that non gravitational heating is negligible for clusters with temperature above \sim 3.5 keV .
The very large scatter observed in the core properties favor scenario where Cooling Flows are periodically erased by merger events .
Our results are consistent with the classical scaling relation between Mass and Temperature ( M \propto T ^ { 3 / 2 } ~ { } ( 1 + z ) ^ { -3 / 2 } ) .
Accordingly the spread in the reduced mass profiles derived from the hydrostatic isothermal \beta –model is small .