Meet the Aprilia RS 660 concept, a mid-weight sportsbike prototype from the Noale-based motorcycle manufacturer. Details are scarce, but Aprilia has revealed some insights into the new RS 660, which Aprilia says is for a 'new generation of riders looking to fulfil thrills on the road as well as on the occasional track day'. Aprilia says the 660 is a parallel twin unit derived from the 1100cc that powered the Tuono 1100 and the RSV4 1100 Factory. Aprilia says this configuration was chosen for its compact nature and efficiency, the extremely low level of heat transmitted to the rider and for the freedom it gives its designers to create a sleek and lightweight frame and suspension. The engine is mated to an aluminium frame and swingarm that helps keep the weight down, and the engine is used as a stress member of the frame. Other noticeable features include the curved shape of the right side of the swingarm, which allows for cleaner exhaust routing, and lack of linkage between the shock absorber and swingarm.