18.0mm outside diameter seat, manifold HF2-LM9 nha is cage 2J641, pn 402190; item is cone shaped on one end for 12mm then tubular shaped for remainder of length with a 13mm dia; inside opening on cone end is 9.6mm dia for 8mm then becomes 6.35mm for 25mm then becomes 1.20mm dia passivate surface treated