One Piece Stretched Smooth Top Steel Gas Tank for FxrGZP FXR gastank +2 single smooth top 4. 2 This one piece stretched smooth top gas tank will give your FXR the long, slippery stretched look and flowing lines as found in our other stretched tanks. The stretched section is not a weld on part but an integral part of the tank and has a seat pocket to match with most narrow seats. Tank will hold approx. 4. 2 gallon of fuel (15,9L.) and is available with single or dual Screw In type gas caps, single or