These only need to be ordered as replacement parts of if you need additional sizes. Alignment and Attachment Plates are sized to the lathe gap. Alignment plates are as wide as the lathe gap and are attached to the steady rest base with 2 5/16-24 set screws not included here. The Attachment Plates overlap the lathe gap and attach the steady to the lathe via a 5/8-18 bolt not included here. Alignment and attachment plates are already included with the Clark Steady Rest. Attachment Plates are included for one lathe with the Clark Deep Hollowing System. For the Sphere Turning Jig, a threaded sleeve is included and the combination is a separate part included with that jig. Sphere Turning Jigs also come with one attachement plate. Purchase these parts only if you desire extra plates for lathes with different gap sizes.