Fluid end manifolds and fluid end manifold assemblies

A fluid end manifold for a reciprocating pump, the fluid end manifold comprising:

• a body comprising:
• a first cylinder bore formed horizontally through the first body;
• a second cylinder bore formed vertically through the first body and intersecting the first cylinder bore to define an intersection region, the intersection region comprising a plurality of contact points where an inner surface of the first cylinder bore contacts an inner surface of the second cylinder bore, wherein the first and second cylinder bores are the only cylinder bores intersecting within the body;
• and
• a ring-shaped first mating face with an outer diameter and an inner diameter disposed along a side of the body and positioned at a location corresponding to the intersection region, wherein the ring-shaped first mating face is formed in a plane that is perpendicular to a plane defining a radial cross section of the first cylindrical bore and to a plane defining a radial cross section of the second cylindrical bore;
• said ring-shaped first mating face operable to connect to a ring-shaped second mating face such that a stress level at the plurality of contact points is reduced while permitting areas of the body inside the inner diameter of the ring-shaped first mating face to flex more than the ring-shaped first mating face.