Built on the technology from the previous design of XTR hubs, the M988 rear disc hubs feature Angular Contact bearings mated to an oversize 14mm alloy axle to support the load of vertical and lateral forces. The Labyrinth sealing system is borrowed from Dura-Ace hubs and is very effective in keeping the bearings fresh and hub internals clean. It is not uncommon to disassemble an XTR hub after seasons of use and find fresh grease - the sealing mechanism really works. The titanium freehub body is light and again, borrowing Dura-Ace technology, the pawl engagement has never been quicker and more precise.
On the cosmetic side of things, gone is the anodized finish and ground polished accents of 970 series hubs. The shells are still black, but now polished for a more classic look. To some degree, it appears the gap is being bridged from XTR to Dura-Ace with the XTR 988 hubs.