Key remote/ immobiliser gubbins

[Stg123]

Good morning ladies and gents, quick question- is the immobiliser "chip" integrated within the remote locking circuit board in our keys, or is it separate, and moulded into the key case itself? Am thinking of changing my key case to an aftermarket one and need to know the answer to this before I go any further.......
Many thanks in advance
Steve

[vw55raz]

the immobiliser chip is in the top half of the key (the flip one). The bottom half of the key is the fob for opening doors remotely.