Abstract: Common component parts for an armature-needle assembly for aftermarket fuel injectors are described herein, where the common components include a needle, an armature, an upper stop flange, a lower stop flange, and one or more guide plates, the flanges and guide plates having apertures configured to accept the needle. The common components are capable of being assembled into at least three different armature-needle assemblies—de-coupled, floating, and fixed configurations. Further included are different sleeve configurations that allow for the adjustment to the induction and the ability to utilize a common solenoid in the different aftermarket fuel injector configurations.