Carbine Vestibule Interior Lever & Exterior Knob SetCarbine 4000 Series interior lever & exterior knob set 127mm backset. Carbine have developed the combination knob and lever set in various functions. It's a combination of the round Sandown 4000 knob series on the outside and the lever of the Rosehill 6000 series on the inside. As such, it is a tiebolt function Function Outside Opened by key only. The outside knob remains rigid Inside Opened by lever at all times Additional Information Fire rated for