Based on the downward-penetrating particle flow through clusters and the analogy between a falling cluster and a rising bubble identified by the authors, a "type-Achoking-oriented separate-phase-coexistence model" for the upper dilute region of fast beds was established first. Without any model parameter adjustment, the unified model predicted successfully the type C choking, the solids holdup of upper dilute region, and transitions to the high-density fast bed and the dense suspension up-flow.The model was then integrated with the sub-models of "cluster rebound at the dense bottom,"" the momentum flux balances for acceleration and transition zones" in the lower and middle parts of the bed. The integrated model predicted successfully the axial solids holdup distributions of literature data under extremely wide operation conditions covering dilute-phase transportation, the premature fast bed, the classical fast bed, and the high-density fast bed.