A. The rectangular cages (Corin). It has wedge shape with larger cranio-caudal diameter in front. The teeth are on the cranio-caudal surfaces. There is a large central cavity which can be filled with bone graft. The cages are designed to be inserted with smaller diameter into the disc space, and then rotated by 90° to orient its long diameter cranio-caudally and to engage the teeth into the endplate. B. The Cylindrical cages (BAK).