They range in size in most species from 50 to 100 centimetres ( 20 to 39 in ) long and can reach in extreme cases up to 2 metres , and 1 to 3 millimetres ( 0.039 to 0.118 in ) in diameter .
They range in size from 50 to 100 centimetres ( 20 to 39 in ) long and can reach in extreme cases up to 2 meters , and they are 1 to 3 millimetres ( 0.039 to 0.118 in ) in diameter .