aperture of sight 观测孔 ; 觇孔

aperture-sight support 觇式瞄准观察镜

sight aperture [军] 觇孔瞄准具

aperture front sight 环形准星

Aperture e sight 觇孔瞄准具

aperture rear-sight disc 觇孔盘

aperture fore-sight disc 准星片

rear sight aperture 觇孔式照门