Topre 2.25U Enter key (R3).  Each available variant is unique and has its own photo.  Please refer to the product photos- this is the cap you will receive.  
 
These caps are cold cast with 320 mesh copper powder mixed 1:1 with resin by weight.  Caps have a forced patina and are sealed using patina sealant.  
 
All caps have Topre stems.