可选部件 meaning in English

selectable unit (su)
su

With the dw rfc tray installed , the following features are added
安装了可选部件之后，可以获得以下功能：
No need of alignment when employing a torque arm ( optional part ) . installation can be compelted only by inserting a driven shaft to the hollow output shaft of the gearmotor
在使用反扭矩杆(可选部件)时无需定位调整，只要将从动插入齿轮减速机的空心输出轴即可完成安装。