We present a study of galaxy sizes in the local Universe as a function of galaxy environment , comparing clusters and the general field .
Galaxies with radii and masses comparable to high-z massive and compact galaxies represent 4.4 % of all galaxies more massive than 3 \times 10 ^ { 10 } M _ { \odot } in the field .
Such galaxies are 3 times more frequent in clusters than in the field .
Most of them are early-type galaxies with intermediate to old stellar populations .
There is a trend of smaller radii for older luminosity-weighted ages at fixed galaxy mass .
We show the relation between size and luminosity-weighted age for galaxies of different stellar masses and in different environments .
We compare with high-z data to quantify the evolution of galaxy sizes .
We find that , once the progenitor bias due to the relation between galaxy size and stellar age is removed , the average amount of size evolution of individual galaxies between high- and low-z is mild , of the order of a factor 1.6 .