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Nanosized SSZ-13 was synthesized hydrothermally by applying N,N,N-trimethyl-1-adamantammonium hydroxide (TMAdaOH) as a structure-directing agent. In the next step, the quantity of TMAdaOH in the initial synthesis mixture of SSZ-13 was reduced by half. Furthermore, we varied the sodium hydroxide concentration. After ion-exchange with copper ions (Cu²⁺ and Cu⁺), the Cu-SSZ-13 catalysts were characterized to explore their framework composition (XRD, solid-state NMR, ICP-OES), texture (N₂-sorption, SEM) and acid/redox properties (FT-IR, TPR-H₂, DR UV-Vis, EPR). Finally, the materials were tested in the selective catalytic reduction of NO<i>_x</i> with ammonia (NH₃-SCR). The main difference between the Cu-SSZ-13 catalysts was the number of Cu²⁺ in the double six-membered ring (6MRs). Such copper species contribute to a high NH₃-SCR activity. Nevertheless, all materials show comparable activity in NH₃-SCR up to 350 °C. Above 350 °C, NO conversion decreased for Cu-SSZ-13(2–4) due to side reaction of NH₃oxidation.