Abstract: There are disclosed several embodiments of an assembly for latching over and sealing about a casing joint having an enlarged diameter upper end so as to install a cementing head or other heavy equipment on the joint. The assembly includes a housing on which the equipment may be mounted and having a bore for lowering over the upper end of the casing joint to connect a bore in the equipment with the casing string. A latch ring is received in a recess in the bore for expansion to permit the upper end of the joint to be moved through and above it, and contraction beneath the lower side of the upper end, and a seal package is mounted in the recess above the ring to seal between the upper end of the casing joint and the recess.