Metric System Pipe Threaded Rod Stainless Steel/carbon steel U Bolts
 
Description:
 
A U-bolt is a bolt in the shape of the U with thread on both ends. It also has square shape.
U-bolts have mainly been used to support pipe use, pipes through which fluids and gasses pass. As such, U-bolts were measured using pipe-work engineering speak. A U-bolt would be described by the size of pipe it was supporting.
For example, a 40 Nominal Bore U-bolt would be asked for by pipe work engineers, and only they would know what that meant. In reality, the 40 nominal bore part bears little resemblance to the size and dimensions of the U-bolt.
The nominal bore of a pipe is actually a measurement of the inside diameter of the pipe. Engineers are interested in this because they design a pipe by the amount of fluid / gas it can transport.
The material can be stainless steel and carbon steel, or we can produce as customer requirements. 
Generally the common material are carbon steel, stainless steel, copper and copper alloys;
Carbon steel bolts in general are: low-carbon steel, a material such as Q235 represented; carbon steel, such as 35, 45 # as the representative of the material; alloy steel, such as chromium and molybdenum as the material 40 representatives.
Stainless steel, as represented 0Cr18Ni9TiMn material.
Copper and copper alloys: copper, brass (H62, H65, H68).