This talk is based on my joint work with I. Penkov. Let g be a simple Lie algebra, and $k$ be a reductive subalgebra in $g. A (g,k)-$module $M$ is bounded if it is locally finite over $k$ and the multiplicities of all irreducible finite-dimensional modules in $M$ are uniformly bounded. (Two examples from classical representation theory are ladder modules in Harish-Chandra theory and cuspidal modules in case when $k$ is a Cartan subalgebra). I will formulate several general results about bounded modules involving primitive ideals theory and geometry (localization). Then I concentrate on the example when $g=B_2$, and $k$ is the principal $sl(2)-$subalgebra, where the complete classification of irreducible simple bounded $(g,k)-$modules is done.