The largest medusas I have (esculenta, inermis, flanaganii) are over a foot wide. E. caput-medusae is another hefty plant. There are medium size plants (like gorgonis and a couple noIDs) which work in 6-8 inch pots.
E. astrophora and decepta (proper) are both really choice medusas on the smaller end. Dial the light up all the way if you can to keep them compact. I have seedling offspring from astrophora which are under 4 inches, and will probably never need a pot bigger than that. One is sterile (never has flowered) so I believe it is a hybrid, and the other made flowers quite unlike the parent, so I know it is a hybrid. The world of medusas is littered with hybrids
E. ramiglans is another one on the smaller side (5-6 inch pot) if size is an issue for you.
A couple of interesting noIDs here in the medium size range. The first has never flowered; the second is self fertile.
