Target gender: Boys We paid particular attention to the accuracy of the center circle, pitch circle, and mating tooth thickness, which can be said to be the lifeblood of spur gears. In particular, the matagi tooth thickness, which requires precision, has achieved the highest precision in the industry!!Film gate molding eliminates uneven filling of the resin and has extremely high roundness, so there is no bending or wobbling. In addition, aiming for the strongest strength, we have developed a special material based on POM with low sliding resistance. It is several times stronger than regular POM spur gears. Inner diameter 9.525mm. (From Discovery Japan Mall)