Hood
The special hoods that come with all these lenses cut out unwanted light and protect the front of the lens from rain, snow, and dust.
To attach the hood, loosen the hood lock knob by turning it counterclockwise. Fit the hood onto the lens's hood mount, and tighten the lock knob to fix it in place. Use the same procedure, in reverse, to remove the hood
Hood ET-120(WII).....EF300mm f/2.8L IS II USM
ET-155(WII).............EF400mm f/2.8L IS II USM