Abstract: A device to couple to a rotatable drill pipe to control pressure of a drilling system is disclosed. The device includes an inner surface to wrap around a portion of a rotatable drill pipe and having an inner diameter. A first tapered portion is opposite a second tapered portion, with a middle portion therebetween including an outer diameter greater than the inner diameter. The first and second tapered portions each taper from the outer surface to the inner surface. The middle portion, the first tapered portion, and the second tapered portion form an outer surface to sealingly pass through a seal element of a controlled-pressure drilling system. At least a portion of the outer surface corresponding to the middle portion includes a low-friction material.