When looking at structural channel materials, you will almost certainly run into the question, "What is the difference between U-Channel and C-Channel?". This is a common question, and the answer is a little more nuanced than one may imagine.
C-Channel and U-Channel tend to be referenced in codes and by manufacturers as the same thing in North America and most other countries, simply being referred to as structural channel.
In Europe, however, codes have been made around C-Channel and U-Channel in an effort to both standardize their applications, as well as reduce confusion when purchasing. U-Channel is referred to as UPE Channel in Europe while C-Channel is referred to as UPN Channel per Standard UNI 5680-73.
The answer to their actual difference lies primarily in the method of manufacturing and intended application of the channel. These differences are due to the materials the channels are manufactured from, as well as the manufacturing processes utilized to create the channel shapes.