A valve cartridge for a fluid end for a well stimulation pump is discussed and illustrated. The valve cartridge optionally includes: a valve body, a spring engaging the valve body on a first side thereof, and a housing at least partially enclosing the valve body and spring. The housing can define one or more passages therethrough. The housing can define one or more seats adjacent the one or more passages. The one or more seats can be configured to be selectively engaged by the valve body on a second side thereof.