If you order this, it actually comes with two of these attachments. One has a slightly smaller opening, presumably for higher magnification objectives. They look to be 3D printed and the finish is a bit rough. There's a rubber gasket inside that helps it slide onto the objective and keep it in place, but for one of them the fit is not very good and it wiggles around a bit. It sometimes comes in handy when you point your light source towards it and the reflection from the attachment gives you sort of a front illumination. But I think, it would be better, if the shape was more concave to direct more light towards the subject. I have recently just taken a piece of thick white foam and cut a hole in it to slide it over the objective, which seems to do an equally ok job.
I have these, and I agree with jnh. It's too dense and not concave enough. It absorbs 4 stops of light at least and light exiting the underside is not broad enough for Mitty working distances, IMO. It's made of robust material (some kind of spun fiber), though. There's about .75cm or so of diffuser material beneath the "stop" shelf for the objective face, and I believe this could cause off-axis light to enter the front of the objective. (The whole thing "lights up" when you put light on the top.) I considered painting (with a sharpie) this part black, as there's not enough room for flocking it without spilling into the line of sight. I also thought about grinding this part away but the nature of the material made me think it would disentegrate. I used it a few times but it's tossed in a drawer, now. The photo shows the "trouble" area I think allows too much off-axis light and creates flare.
These things were not designed to serve as diffusers for light going through them from the lens side.
Instead they are diffuse reflectors, along the line of Lieberkuhn reflectors. They are intended to be used with flashes that are mounted beside the specimen, emitting light in the direction of the lens.
Makes perfect sense, now. Thanks for the info and link. Now, how can I modify it to ..........? Half the fun of this hobby is finding ways to repurpose things for it. Especially things just lying around.
A nicer and way cheaper method is ping pong balls. With one ball, you get 2 diffusers. The logo can usually be wiped off using those strong adhesive removers. Get yourself a pair of cheap ebay surgical scissors and trim away.
Thanks for all the comments, appreciated. I guess its either up to the attic and grab some ping-pong balls, or its back to the kitchen for empty yogurt containers
It's not what you look at that matters, it's what you see - Henry David Thoreau