A disk brake for a utility vehicle, having a brake calliper that comprises a brake disk and is fastened by two fastening elements to a positionally fixed brake carrier so as to be axially displaceable in relation to the brake disk, the fastening elements each having a guide bar that is permanently connected to the brake carrier, in order to ensure the axial displaceability of the brake calliper one of these guide bars being mounted as a fixed bearing the other being mounted in a sliding bearing that takes the form of a floating bearing has a floating bearing axis, at least the floating bearing having a guide bush that encompasses the guide bar and is held, secured against displacement, in a calliper bore of the brake calliper, there being arranged at least at the end region of the guide bar facing away from the brake disk a first variable-length tubular seal that seals the guide bar against the environment and is fastened on one hand on the guide bar and on the other in the guide bush, this first variable-length tubular seal being clamped on the guide bar by means of a cap that is pressed into the guide bar, the first variable-length tubular seal having a ring portion that is placed in a peripheral groove between a covering portion, a collar and a portion of a peripheral outer surface, this ring portion being held such that it is secured radially inwards in relation to the floating bearing axis by the portion of the outer surface and being held such that it is secured radially outwards in relation to the floating bearing axis by the covering portion, the collar being integrally formed on an end of the cap facing away from the brake disk, and the outer surface being a peripheral outer surface of a cylindrical body of the cap, a peripheral groove taking the form of an annular groove between an underside of the covering portion, an inside of the collar and the outer surface, the covering portion being attached to the outer radial end of the collar of the cap and extending towards the brake disk axially parallel to the floating bearing axis, the ring portion being pre-tensioned axially directly or indirectly against the guide bar in the peripheral groove, characterised in that the ring portion is connected axially to a peripheral web that is in contact with a peripheral end face of the guide bar. the first variable-length tubular seal having a ring portion that is placed in a peripheral groove between a covering portion, a collar and a portion of a peripheral outer surface, this ring portion being held such that it is secured radially inwards in relation to the floating bearing axis by the portion of the outer surface and being held such that it is secured radially outwards in relation to the floating bearing axis by the covering portion, the collar being integrally formed on an end of the cap facing away from the brake disk, and the outer surface being a peripheral outer surface of a cylindrical body of the cap, a peripheral groove taking the form of an annular groove between an underside of the covering portion, an inside of the collar and the outer surface, the covering portion being attached to the outer radial end of the collar of the cap and extending towards the brake disk axially parallel to the floating bearing axis, the ring portion being pre-tensioned axially directly or indirectly against the guide bar in the peripheral groove, characterised in that the ring portion is connected axially to a peripheral web that is in contact with a peripheral end face of the guide bar.