Top sleeve rubbers are shock-absorbing buffer items that are used in the Jumbo series of brick machines. They are used to secure the top sleeve and minimise the vibration translating from the guide shafts to the machine frame.
 
Whilst the item itself doesn't experience abrasive force particularly, the rubber is usually compressed tightly to keep the top sleeve steady to receive the guide shaft stopper nuts. The cyclical repetition of stopping the weight of the stamper unit means daily contraction & expansion which naturally denatures the top sleeve rubber and ultimately requires replacement.
 
Four (4) are used per brick-making machine - Keep several of these rubbers as consumable replacements.
 
This is not the mounting rubber used on the vibration table.