The Sargent 8237 LNL 26D is a Grade 1 Heavy Duty Classroom Function Mortise Lock with an LN Rose, an L Lever, a LA Keyway, Keyed Random and comes in a Satin Chrome Finish. Sargent 8237 LNL 26D has a 2-3/4" backset, and is for use on 1-3/4" thick doors.