Kore Pre-Teen Active Chair - 18.7" Academic Choice Award Winner! Suggested for ages 10-11; Grades 5-6; Child height 54 in. to 57 in. Anti-Roll Safety-A patented anti-roll safety ring on the base prevents tip-overs and falls. Manufactured with Antimicrobial Protection against the spread of common bacteria; FDA approved and successfully tested to reduce up to 99.9 percent of common bacteria including E. Coli, Listeria, and S. Aureus. Gently rounded ergonomic base allows you to move and flex without leaving your seat. Exercises legs, back, and abdominal muscles. Great for doing homework and playing video games. Easy 2 minute assembly. Seat Diameter 11” / 28 CMBase Diameter 13.75”/ 35 cm Stool height (top of seat to floor) 18.7 47.5 cm