The Mortise Lockset is very similar to the Marks 22AC3 and can be used in most security doors that use the Marks. The pluses are: Telescoping Collars and SC1 cylinders allowing for keying with Schlage Locks. There are some differences: Handing can be changed so check that the handing you purchased matches what you need. May need to use tailpieces on SC1 cylinders if you plan to use other cylinders as standard tailpieces may not retract latch. Knobs made in two parts and knob can at times slip when turned too hard or if lock or stopworks is locked. Good replacement at better price with limitations above. Parts may not interchange with Marks parts. 3.5 stars.