The manufacturer says: "The Standard Horizon HAC-15 is a fifteen-station vertical friction-feed collator that can be expanded to four towers for up to 60 feed stations. The HAC-15 has powerful programming options, and represents the most feed stations available in a small footprint configuration. The HAC-15 accepts all Standard Horizon heavy-duty accessories."
We have three of these units, which can be combined to offer 45 stations, all under computer control.