We discuss a recently introduced real space renormalization group (RSRG) approach. Unlike other RSRGs, it does not depend upon weight functions arisen from particular recipes like majority rule or others. Instead, it is formulated assuming only the validity of Fisher's finite size scaling hypothesis. Because of this, it is free from conceptual criticisms normally invoked against RSRGs, as well as other unpleasant consequences of particular weight function choices as the so-called proliferation of parameters, for instance. Simple exact calculations can be performed for small lattice sizes, yielding qualitative informations and reasonably accurate quantitative critical frontiers and exponents. Very accurate values can be obtained, however, performing the same calculations for larger lattices, using Monte Carlo sampling.
