短语词组短语Pull Back Power ring 倒后擦发条BACK UP RING KIT 备份环套件;备份圆环套件back support ring 后支承环Back up ring 支承环back sealing ring 后密封环back moving ring 回位弹簧back locating ring 后定位环back contact ring 静接点弹簧 返回 back ring