In one example, a system is provided, comprising an exhaust reductant injector upstream of a mixer. The mixer includes a plurality of concentrically smaller rings interconnected via fins having a width varying in a flow direction, the fins arranged annularly, and with a first set of fins between a first pair of adjacent rings angularly offset from a second set of fins between a second pair of adjacent rings, the first and second pairs of rings sharing one common ring. In this way, it is possible to atomize, redirect, and mix the exhaust flow over a short distance to effectively react with NOx in a downstream SCR catalyst.