While it would be much larger than needed for your camera/lens combination, if you own the larger Canon EF 400mm f/2.8L IS II USM lens, the Canon EF 500mm f/4L IS II USM, lens, the Canon EF 600mm f/4L IS II USM lens, or the EF 800mm f/5.6L IS USM lens, and you wish to use the larger Canon ERC-E5L Rain Cover (Large) with your Canon EOS 90D DSLR Camera and your Canon EF 100-400mm f/4.5-5.6L IS II USM Lens, this setup would work for your usage needs. Otherwise, if the Canon EF 100-400mm f/4.5-5.6L IS II USM Lens is the largest lens you own, I would instead recommend the smaller Canon ERC-E5S Rain Cover (Small), B&H # CAERCE5S, for your usage needs. https://bhpho.to/3PRMwqj

The Canon ERC-E5L Rain Cover has a large transparent window that allows viewing of the LCD monitor. The included, Eyecup L and Eyecup S, will replace the one on the camera to fit all EOS cameras over the cover.

For the Canon R5 with a 24-70mm lens attached, the Canon ERC-E5L Rain Cover (Large) will work, but it's going to be too big. You may want to consider the smaller size, which can be found at this link: https://bhpho.to/3zGqmlJ.

The Canon ERC-E5L Rain Cover (Large) would be to large for the Canon EOS 5D Mark III DSLR Camera with the Canon EF 300mm f/4L IS USM Lens. The recommended cover for that setup is the Canon ERC-E5S Rain Cover (Small), BH #CAERCE5S (https://bhpho.to/4abP8Hv).

It is not compatible with the R3. The viewfinder attachment if different.

This rain cover requires the removal of the outer eye pierce to fit over the view finder. Since the mirroless camera are screwed into place it does not fit. Have not been brave enough to take the screws out and remove the soft part of the eye prince to see if it will work.

It works with:- 200mm 1.8/2.0- 300mm 2.8it dont works with- 70-200mm 2.8 - 100-400mm 4.5-5.6'cause the diameter of the lens hood is too small, the velcro don't fix.