This is an item to help children run faster. I bought it for my child who was playing soccer and used it a few times. It's the perfect item for children who want to run faster. ※This is a rare item that is currently not for sale. Mizuno mizuno C3JET55200 Kids' Running Form Correction Supporter Dash Driver SP Tax included: 3,850 yen Practice using the Dash Driver The sound won't rhythmically ring if the elbows are extended or the arms aren't swinging correctly. Practice running with bent elbows and large arm swings so that the sound rings rhythmically. Once you get the hang of the rhythmic sound, your running speed will increase. 58% of kids' form improved immediately As a result of having 24 boys and girls aged 5-7 who couldn't swing their arms correctly practice running with the Dash Driver, 58% of the kids' form improved immediately. ※According to Mizuno