The shuttle, which is the “extension” for the shock to get it to the correct length to generate the correct wheel rate vs travel has two bearings, a cross tube, and two “end caps”. The bearings are press fit, and “Capture” the cross tube between them when they are pressed in. The end caps ensure the centre of the bearings is preloaded correctly. You will need the end caps and cross tube, the bearings are std 2RS bearings (sorry, can’t remember exact size at the moment). Hotlines should be able to source those for you, but be prepared for a wait ime…..
Of course you can just reuse you existing end caps and cross tube in the new shuttle. Even though i ended up with both, thinking i could swap between 140mm & 160mm easy, the bike rides so well at 160mm i’ve never swapped back in just over 2 years……… 😉