PROLINE Pnuematic Internal Line Up Clamps assure a rapid, accurate alignment of two joints of pipe during the welding operation. Front and rear heads operate independently to lock the clamp into position. Specially designed shoes on each head exert pressure uniformly around the inside circumference of the pipe to maintain necessary alignment. Each Lineup Clamp is quickly and easily adjusted for different pipe wall thickness. Clamps 16″ (406.4 mm) or larger are self-propelled with powerful air motors that drive the clamp forward through the pipe to the next joint. PROLINE clamps have been proven in thousands of miles of pipeline construction, under the most extreme field conditions.