Drop-in diffusers are the most popular style of diffuser because they are available for a much wider range of shades than the other styles of diffuser. Any shade of 12" / 30cm diameter or more can be fitted with a diffuser (and these can be retro-fitted if you are sure on the diameter of your existing shade).
The To fit 12" Shade is not in stock and will be made for you. This can take up to 5 weeks.
These diffusers are 2" less in diameter than the diameter of the shade and are held up just inside the bottom rim by little metal clips integrated into the shade frame. So these cannot be retro-fitted and must be ordered at the same time as the shade is ordered. The lower part of the clip will be visible when the shade is hung, but they are very discreet.
These are only available for shades 20" (50cm) in diameter or larger.
The To fit 20" Shade is not in stock and will be made for you. This can take up to 5 weeks.
These diffusers hang from the same lampholder (or lampsocket) as your shade and sit about 25mm above the bottom rim of the shade, so are suspended higher up in the shade. They are 6 inches (9cm) smaller in diameter than the shade itself so that plenty of light passes around the diffuser while still blocking the direct light from the bulb.
These are only available for shades 20" (50cm) or more in diameter.
The To fit 20" Shade is not in stock and will be made for you. This can take up to 5 weeks.