Glad to meet another MF3D shooter!

As far as I know, 3D world is defunct and nobody produces plastic mounts for medium format stereo slides. I make  cardboard mounts that are essentially copies of the mounts formerly sold by Rocky Mountain Memories. The outer dimensions are 80 mm x 132 mm (versus the 80 mm x 140 mm previously offered by 3D World.) The apertures are 50 mm square an separated by a distance of 62 mm. I also offer 3 different cropped aperture mounts. You can find all the details on my website:

My offer to you and anyone else reading this message is a (free) sample of one of each of the 4 types of mounts so you can see if they are what you are looking for.

I am currently on vacation in Utah (along with my Sputnik), so I won't be able to ship any orders until Friday.

All the best,

Ian