A new 36.71Wh cell for the 2018 12.9-inch Pro - the redesigned, Face ID, USB-C generation.
Service Details
The 2018 redesign dropped to a 36.71 watt-hour cell in a noticeably thinner body, swapped Lightning for USB-C, and put Face ID where the home button used to be. All three matter here: the case has less give, the TrueDepth cable runs along the top of the display, and the panel is bonded - so the way in is planned rather than forced.
New cell, new adhesive, resealed, then Face ID, USB-C charging and the ProMotion refresh checked before handover. A thin chassis is also the reason a swelling cell on this model shows itself early, as a lifted corner.