9000 brake lever part question

[Kingfisher]

Is the plastic part in the photo necessary for proper shifting/braking? Pic is of the right lever, the gray plastic piece broke off on the left lever.

[oldpotatoe]

Is the plastic part in the photo necessary for proper shifting/braking? Pic is of the right lever, the gray plastic piece broke off on the left lever.

It works in conjunction with the ferrules to allow for smooth exit of the cable and housing from the lever...really ought to use it, replace it.

Part numbers
Y63X55000
Y00F75000

http://si.shimano.com/#/en/search/Component?name=Shift%2FBrake%20Lever&type=ROAD