The objective of the article is to show the phenomenon of the internal standardization of the units of the Polish cavalry in the 16th century. The references to this process, during which the diversisty of arms and equipment of soldiers was abandoned, are scarce in descriptive sources and are only reflected in normative acts. The only type of sources which enables to reconstruct the combat potential of units is inspection (rejestry popisowe). Consequently, the process of specialization of units and of formation of different types of cavalry was basically marginalized. In the Crown, as late as the 1530s, cavalry rotas were very diverse. They consisted of lancers, Polish winged hussars (later: hussars) and light cavalry combined in various proportions. This state of affairs is connected with three factors. Firstly, the units of Permanent Defense (obrona potoczna) in their structure referred to Mass Mobilization (pospolite ruszenie). Secondly, provisions of law were not used for standardizing the arms and armor; on the contrary, at least by the 1530s they stimulated the internal diversification. Thirdly, the Crown professional units were internally divided into towarzyszes and pocztowys, which prompted the diversification of armament inside a unit. The text shows the changes which occurred in the 1540s and 1550s, and brought about a situation in 1557, when the rate of standardization was as high as 82.93 %. The transformations were dynamic but were not top-down planned reforms, representing instead a bottom-up initiative of rotmistrzes.