Kelly hose is used to connect the standpipe to the swivel. It allows the drill string to be raised and lowered while the drill fluid is pumped through it. Kelly line usually contains two layers of plated steel cables to reach 5000 psi operating pressure. Inside tube is made of special NBR to improve abrasion and corrosion capability. Rubber cover is compatible with the ozone, sunlight and oils for a long time. It is supplied with multiple end fittings – API flanges, threads, butt-welded union and other as specified.