The Seiko 3B21-0AK0 is a watch model based on the 3B21 movement.
Parts List
| D3D3AB | band - metal band |
| D3D3AB-LK00 | band - link |
| D3D3AB-BK00 | clasp - clasp |
| D3D3AB-BKLK-12H | clasp - parts for buckle/clasp |
| D3D3AB-BKLK-6H | clasp - parts for buckle/clasp |
| D3D3AB-BKPN | others - pin for buckle/clasp |
| D3D3AB-BKPP | others - spring bar for buckle/clasp |
| D3D3AB-EP00 | others - endpiece |
| D3D3AB-LKPN | others - pin for link |
| 81604259 | others - bracelet fixing pin |
| 81190055 | others - bracelet fixing pipe |