It's my understanding that the sterilite 1755's replace the 1756. Or at least, I hope so, as I have a couple unassembled 1756 AP racks in storage and a pile of 1755 boxes. The others I'm not sure on. I'm sure Ali at AP would be happy to help if you email them.

From now on, I'll be buying the Iris racks. Iris seems far less inclined to discontinue tubs frequently.