This JET Rail Bearing shows the scraper option which clears the shaft of debris in front of the top, load bearing roller. Unlike linear ball bearings where the shaft is in direct contact with the shaft - allowing debris to get beneath the seal and into the ball tracks ( causing bearing failure and shaft grooving ) - Jet Rail roller seals are not in contact with the shaft. Subsequently, JET Rail greatly inhibits internal roller failure and will not groove shafting.