advance variable backcheck

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AVB stands for Advanced Variable Backcheck. It is a cylinder option when ordering a 4111 closer (without an ST) that allows backcheck to start at about 45 degrees instead of the normal 75 degrees. ...
AVB, Cylinder Function, 4110 Series Closer
A 4110 with AVB (advance variable back check) would be recommended. Using a SCUSH (Spring Cush) arm will also help minimize shock to all door hardware.
 The Y latches listed below are adjustable to fit either a 2 3/8" or 2 3/4" backset. LATCHES WITH LOCKS  Description  Backset  Specify  Square corner, 1-1/8" x 2-1/4", standard  2...
 The latches for the Y and F lock are not interchangeable as the hole sizes are different. Substituting any latch voids your UL and product warranty. 
Advanced Variable Backcheck