Numatic NUC244NX Chuck/Drive O-ring Replacement Kit with Grease 915735 NUC244,
This part is known as 915735. NUC244NX, NUC244NX-R, NUC244NX-RHM, NUC440, NUC440HM. This is a Genuine Numatic part. These O-rings are located on the bottom of the left and right hand chucks, and help hold the drive boards in place.