speed ring sight[航] 航速显示瞄准环
ring sight pointer环形指示器
Ghost ring sight鬼环式瞄准具
ring and bead sight圆环与准星瞄准具
A CRYSTAL RING SIGHT晶体光环瞄准镜
bank ring sight环状坡度指示器
Ghost t ring sight鬼环式瞄准具
optical ring and bead sight光学环形瞄准器及准星
front sight ring准星护圈