The aim of this experiment is to study the effect of Sn and Oxygen on deformation mechanisms in Zr alloys with a particular emphasis on studying twinning. Both alloying elements are found in many commercial Zr alloys used by the nuclear industry. Zr alloys are used as cladding material for nuclear fuel and are in principle seamless that encapsulate UO2 fuel pellets. An important aspect of the cladding material is the crystallographic texture of the tubes. The most desirable texture is a radial basal texture, because of the way hydrides form during service. The generation of this texture is closely linked with twinning, as the most common twinning mode rotates the c-axis in the compressive loading direction. Therefore understanding twinning and the effect of alloying elements on twin nucleation is of great importance in order to develop plasticity models for texture predictions