A block fitting for a fluid system comprising: a male block including a bore extending therethrough adapted for connection to the fluid system; a female block including a bore extending therethrough adapted for connection to the fluid system; the male block having a radial annular surface surrounding the bore and a planar longitudinal inner end surface facing the female block, the male block defining a shoulder projecting longitudinally from the planar longitudinal inner end surface, the shoulder defining a reduced diameter cylindrical surface and an annular step surface; a polymeric guide sleeve (156, 256) defining an inner cylindrical surface surrounding the radial annular surface of the male block, the guide sleeve (156, 256) supported on the reduced diameter cylindrical surface of the shoulder of the male block; the female block having a radial annular surface surrounding the bore, an annular groove surrounding the radial annular surface, the annular groove defining a cylindrical surface facing radially inwardly; the male block and female block joined together with the bores (40, 62) aligned and the radial annular surface of the male block 30 and the radial annular surface of the female block spaced apart in facing relation; a primary seal member having an annular body portion disposed between the radial annular surfaces (46, 76) of the blocks (30, 60) surrounded by the inner cylindrical surface of the guide sleeve (156, 256); and a secondary seal member spaced apart from the primary seal member and positioned between the cylindrical surface of the female block and the reduced diameter cylindrical surface and annular step surface of the male block, for compression when the male block and female block are secured together. a male block including a bore extending therethrough adapted for connection to the fluid system; a female block including a bore extending therethrough adapted for connection to the fluid system; the male block having a radial annular surface surrounding the bore and a planar longitudinal inner end surface facing the female block, the male block defining a shoulder projecting longitudinally from the planar longitudinal inner end surface, the shoulder defining a reduced diameter cylindrical surface and an annular step surface; a polymeric guide sleeve (156, 256) defining an inner cylindrical surface surrounding the radial annular surface of the male block, the guide sleeve (156, 256) supported on the reduced diameter cylindrical surface of the shoulder of the male block; the female block having a radial annular surface surrounding the bore, an annular groove surrounding the radial annular surface, the annular groove defining a cylindrical surface facing radially inwardly; the male block and female block joined together with the bores (40, 62) aligned and the radial annular surface of the male block 30 and the radial annular surface of the female block spaced apart in facing relation; a primary seal member having an annular body portion disposed between the radial annular surfaces (46, 76) of the blocks (30, 60) surrounded by the inner cylindrical surface of the guide sleeve (156, 256); and a secondary seal member spaced apart from the primary seal member and positioned between the cylindrical surface of the female block and the reduced diameter cylindrical surface and annular step surface of the male block, for compression when the male block and female block are secured together.