An assembly of components used to contain wellhead fluids and pressure during braided-line or wireline operations. The wireline passes through a close-tolerance tube assembly as it leaves the wellbore. High-pressure grease is pumped into the surrounding annulus to effect a pressure-tight dynamic seal that is maintained during the operation by injecting more grease as required. A slight leakage of grease is normal, and the addition of fresh grease enables the consistency of the seal to be maintained at an effective level.