Hmm, I always buy the largest size thinking it's cheaper, but buying a smaller size for the containers ... that's a good idea!
The large ones are OK for holding compost ingredients next to the sink (I cut the top inch off so that the threaded lip doesn't get in the way when I dump it out).
BTW, I bought some seed-starting trays with 200 cells because i read that was a good way to start lots of lettuce. But they make GREAT pen-and-pencil holders when cut into blocks of 5x4 cells! One or two pens in each cell. Probably most people could make do with a 3x4 block of cells, but it might be tippy.
