These units are designed to have a large 2.5" lead screw running through each one. With all 4 or the input drive shafts mechanically linked together and driven by a gear motor or hand crank, all 4 units will move together such as to raise and lower a platform.  A common application we have seen is for raising and lowering the anvil of a big hydraulic press.

 

While two have one brand name and 2 have another, they all have the same model number.  The only difference seems to be a green collar mounted on top the green labeled ones.