eBay

Brand new, old-stock drop-in gelatin filter holder. Retail price is $180.

This will fit the following lenses:

• EF 300mm f/2.8L

• EF 300mm f/2.8L IS

• EF 300mm f/2.8L IS II

• EF 400mm f/2.8L

• EF 400mm f/2.8L IS

• EF 400mm f/2.8L IS II

• EF 400mm f/2.8L IS III

• RF 400mm f/2.8L IS

• EF 500mm f/4L IS

• EF 500mm f/4L IS II

• EF 600mm f/4L

• EF 600mm f/4L IS

• EF 600mm f/4L IS II

• EF 600mm f/4L IS III

• RF 600mm f/4L IS