The G4110 is a 12.5" extension that can be used with the Gateway pressure mount gate. Please see the guide below to find out how many extensions you will need based on the width of your opening. There is overlap in the measurements to account for uneven surfaces.
Gateway Extension Placement Guide
31.5" - 37" Included with gate
37" - 42.5" 1-G4100
42.5" - 47.5" 2-G4100
47.5" - 49.5" 1-G4110
49.5" - 55" 1-G4110 + 1-G4100
55" - 62" 2-G4110
62" - 68" 2-G4110 + 1-G4100
68" - 73.5" 2-G4110 + 2-G4100