A block fitting for an air conditioning system includes a male block portion and a female block portion. The male block portion has a first annular pilot. The female block portion has a first annular collar that receives the first annular pilot of the male block portion. The first aperture of the male block portion and the first aperture of the female block portion are substantially concentrically aligned. A first seal structure is disposed between the first annular pilot of the male block portion and the first annular collar of the female block portion. A fastener engages the male block portion with the female block portion to form a substantially fluid tight seal. One of the of the male block portion and the female block portion has a stabilizing heel formed adjacent a side surface thereof. The stabilizing heel militates against transverse dynamic loading of the seal structure in operation.