Abstract: Sealing means for telescopically related elements, especially elements such as the bit shank and body of a fluid-powered free piston hammer drill, comprise a diametrically divided sealing ring dimensioned to run sealingly and circumferentially uninterruptedly on a cylindrical sealing surface on one of the elements (e.g. the bit shank of a hammer drill) and sealingly to engage the other of the elements (e.g. the drill body). The sealing ring may be constructed of any material suited to its duty. If it is to perform a retaining function by limiting relative motion of the elements it may be of steel or other hard and strong material and may if required have a flexible or elastomeric sealing element.