Disclosed is an apparatus for injecting a plurality of uniform jets into an extended dispersion of moving catalyst particles within a reactor vessel. The apparatus comprises a plurality of outer conduits each for carrying contacting fluid and being fixed to a respective opening in a first tube sheet. A plurality of outlet nozzles are each fixed to a respective opening in a second tube sheet which is fixed to the first tube sheet. Feed in the outer conduits are delivered to the outlet nozzles for distribution into the vessel. All of the outlet nozzles can be easily replaced by breaking the fixation between the two tube sheets and securing a new second tube sheet with outlet nozzles to the first tube sheet.