Heavy wall reaction flask with jacket, part of the two-piece pressure reactor, for use at elevated pressures. Duran type top flange supplied with O-Ring groove for use with heads 6433, 6527, 6528 or 6529. Cooling/heating jacket is heat sealed. Inlet/outlet on jacket has size 28/15 O-Ring ball joints with size -116 FETFE O-Rings. Uses 6517 quick-release clamp.