Reversible computers usually work in a synchronous mode, i.e., in the presence of clock signals, but in the light of the asynchronous nature of microscopic physical phenomena this may be an anomaly. The alternative, an asynchronous mode of operation, has therefore attracted attention from researchers, witness the proposal of a reversible circuit element in (Morita 2001) that works in such a mode. Simplicity of circuit elements like this is an important design objective since it correlates positively with the efficiency by which they may be realized physically. In this paper, we present two mutually inverse logic elements that compare favorably to other circuit elements in terms of their number of states and their number of input and output lines. We show that the proposed circuit elements can perform universal computation by embedding circuits made of them in asynchronous cellular automata.