This industry comprises establishments primarily engaged in the merchant wholesale distribution of supplies for machinery and equipment generally used in manufacturing, oil well, and warehousing activities. Merchant wholesale distribution of hydraulic and pneumatic (fluid power) pumps, motors, pistons, and valves--are classified in Industry 423830, Industrial Machinery and Equipment Merchant Wholesalers; and Merchant wholesale distribution of welding gases--are classified in Industry 424690, Other Chemical and Allied Products Merchant Wholesalers.