Rectangular steel pipe EN 10305-5 (DIN2395) Also known as precision steel pipes. The steel pipe is of great accuracy regarding the dimensions and has a very fine surface. We use steel pipes to reinforce the X-axis construction on our machines. The gap between the aluminum profiles are exactly 60mm so that the tube can fit. Please note that the dimensions can vary about 2mm in ends. The freight is expensive when we send steel, but we only take out the actual cost. Buy this locally if possible.