Build your own Suspension. Circuit Coilover Parts Now Available.  The Circuit Coilovers feature a single spring design which gives an aggressive feel which may be commonly seen on fully threaded shock coilovers.  Now you can have the features of a fully treaded shock without the big price tag. By offering the sleeve and spring portion of the coilover, you have the choice of your shock combo, whether it be an adjustable shock or regular high performance shocks.