Rugged spherical reaction flask with Duran style flat flange with O-Ring groove, for use with 6517 Quick Release Clamp. Various valve and bottom fitting configurations available, see individual listings. each flask includes a CAPFE (PTFE encapsulated silicone) O-Ring. Plain silicon O-Rings are also available. See 6472-69, -99 and -245 for valves. For reaction heads see 6528, 6529, 6530, 12860, 12862 and 12864. For cooling/heating coils see 12067. For heating mantles see 12044.Bottom valve has an O-Ring ball joint connection on stem.,/P.