These convenient height extension kits easily convert Alvin’s office-height chairs into drafting height models. Each kit includes a strong cylindrical steel shaft with tapered end to lock into the chair base. Adds approximately 7½" to the height of the chair. Foot ring models can be adjusted vertically and then locked at the desired height. It is recommended that extension kits be attached when the chair is first assembled. Extension kits fit the following chair models: CH277, CH290, CH444, CH555, DC205 and DC207B.