National Oilwell Varco acquired Russell Sub Surface Systems (RSS) in 1998. National Oilwell Varco's RSS group designs and manufactures steering tools and downhole sensors which provide accurate and reliable information on inclination, azimuth, pressure, temperature and weight on bit, and more recently directional sensors for MWD applications. Such information is critical in directional drilling. National Oilwell Varco also provides product training, customer calibration of equipment, software development, engineering, testing and product qualification services for directional tool customers.