Lock Knob Nut for Lens Hood ET - 155 Canon EF (RF) 400mm f/2.8L IS II / III USM
This is non-Canon alternative Lock Knob Nut for Lens Hood ET-155 Canon EF (RF) 400mm f/2.8L IS II / III USM. This isn't a Canon part or in anyway a copy of the original but fully replaces the 7 parts which make up the OEM knob.