What do "SIM", "HIM", and "NIM" mean in foreign trade chemical fiber? SIM: light terminating led, meaning light mesh. A synthetic fiber with 40-50 knots per meter is called a lightweight net, which has a low network fastness and is easy to disperse when pulled by hand. HIM: high terminating led, meaning heavy network. A synthetic fiber with 100-120 knots per meter is called a heavy net. This type of synthetic fiber has a high network fastness and is not easily pulled apart by hand. NIM: non interlaced, meaning no network. A synthetic fiber with 0-10 knots per meter is called a meshless fiber. This type of fiber has no network points and has the lowest network fastness. It will scatter when pulled by hand. These terms are mainly used to describe the network structure of synthetic fibers, helping to distinguish between fibers with different network fastness and meet different usage needs