The G4100 is a 5.5″ extension that can be used with the Gateway Pressure Plus and Auto Close Gateway pressure mount gates. 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. Available In: White G4100 Black G4101 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 Auto Close Gateway Extension Placement Guide 31.5″ – 37″ Included with gate 37″ – 42.5″ 1-G4100 42.5″ – 47.5″ 2-G4100