The hardpoint's diameter is defined by the inner diameter, as seen in the image.

挂载点的直径就是指它的内径，如上图。

This refers to the use of a miniature BTE hearing aid that is coupled to an ear insert or earmold (vented or unvented) via a tubing of approximately 0.8 mm inner diameter.

就是微型耳背式助听器用一根内径大约0.8毫米的细导管耦合到耳塞或者耳模（耳模可以开或者不开通气孔）的验配方式。