Mask chain adopts the SCM alloy steel, pass the special Carburized Nitrogen heat treatment, its intention power is much higher than general roller chain 850 kgf, totally accords with ISO and JIS industrial standard. The straight shape design of outside chain plate offers the ability of Freestyle bicycle to use the roller chain to collide ability of Freestyle bicycle to use the roller chain to collide against any object, smooth-going instead of beating, have more comfortable and safer assurance to ride persons who take advantage of it.