All pipe is to be made of a long hole, surrounded by metal or plastic centred around the hole.
Some vendors are now able to supply pre-rusted pipe. Flanges must be used on all pipe. Flanges must have holes for bolts, and these holes must be quite separate from the big hole in the middle. Be sure to specify whether you want level, uphill or downhill pipe. If you use downhill pipe for going uphill, the water will flow the wrong way.