ZB is the classic long-duration rate contract. Its deliverable basket covers bonds with 15 to 25 years remaining, which is why the separate ultra bond contract was created for the true 30-year sector.
Its high duration makes it the most price-sensitive of the mainstream Treasury contracts, and the usual choice for expressing a view on long-term inflation and term premium rather than on Federal Reserve policy.
Example: ZB quoted 118'16 means 118 and 16/32, or $118,500 per contract. A one-point move is $1,000. With a dv01 near $190, a 25-basis-point yield move is worth roughly $4,750 per contract.
Related: treasury-futures, ultra-bond-futures, zn, dv01, thirty-seconds-pricing