In this paper we study relations between the left-right-measure and properties of singular masas. Part of the analysis is mainly concerned with masas for which the left-right-measure is the class of product measure. We provide examples of Tauer masas in the hyperfinite II1 factor whose left-right-measure is the class of Lebesgue measure. We show that for each subset S ⊆N, there exist uncountably many pairwise non conjugate singular masas in the free group factors with Pukanszky invariant SU ∞. © 2013 University of Houston.