8120 x 1. Used on all  XK120 & XK140 & XK150 models except if AC Fuel filter fitted , that use : 8121. It is a stainless steel braided flexible pipe in the fuel line that takes up the movement between the carb feed pipe on the engine and the fixed petrol pipes on the body. As it is constantly moving, this should be checked regularly to ensure it has not fractured from wear or age. Original Ref. C3629

Note: XK150 models with fuel filters also use a version of this, but  with a fixed banjo onto it, our Part : 8121 which bolts directly to the fuel filter head.

8120 is then used further down the fuel line towards the body.