New German made Siebenrock oil resistant clutch friction disc for all R850/1100 bikes built from 12/97 and later(except R1100S). These clutch plates are treated with a high tech coating that makes them impervious to oil. If your clutch is fouled by a leaky main seal or clutch slave cylinder you can keep riding without the clutch being ruined. The friction material can handle considerably more torque than the OEM disc and for many riders will last the life of their bike.
BMW and Siebenrock both recommend replacing all clutch components (pressure plate, cover plate, diaphragm spring and clutch bolts) when installing a new friction disc. If your clutch parts are worn unevenly and you install a new friction disc without replacing the other clutch parts you risk damaging the new friction disc and severely shortening the life of the new friction disc.