Latest addition to the prox program is the exhaust valve & spring kits.This kit is offered as an alternative where the oem application uses titanium valves.Prox has now developed the exhaust valve & spring kits, containing a set of steel intake or exhaust valves plus a set of specially designed stronger valve springs.The prox kit just replaces the oem valves & valve springs and can be installed using the oem retainers, bases and valve seals.