The update is the Mac Pro EFI Firmware Update 2.0 and was released just recently and weighs in at around 5MB, making it a small but recommended update as Apple claims that the update will help improve system reliability during the rebooting process. The update is also said to resolve an issue related to memory self-test, and will also aid in improving graphics power management when using Boot Camp.
The latest Mac Pro is the long-awaited successor to its predecessor which remain relatively unchanged for a couple of years. Its design, while unique, is somewhat controversial, along with its price tag where Apple is asking for $2,999 for the base model, making it a rather expensive purchase.