An optional Extra-Long (XL) Seat Post with Performance Seat can be purchased to accommodate even more growth of your rider. The Standard Seat Post that comes with the Strider 12 provides a seat height range of 11-17 in. (28-43 cm) fitting rider inseam measurements of 12-18 in. (31-46 cm). The XL Seat Post plus Performance Seat provides a seat height range of 15-19 in (38-48 cm) fitting rider inseam measurements of 16-20 in. (41-51 cm).