Felting needles are used to mechanically intertwine fibers in a needle loom. They accomplish this by catching fibers in barbs located on the edges of the working blade area of the needle. In the picture supplied by Foster Needle Co. you can see two types of needles. The needle on the right has a middle section that is thinner and allows the needle to bend more without breaking. Most needles are 3” or 3 1/2” long and are 15 gage in diameter where they fit in the hole in the board. 15 ga. Is 0.0720 inches in diameter. There are two primary needle manufacturers, Groz-Beckert and Foster Needle Company.