Tripled walled, quartz, immersion well for use in temperatures as low as -78ºC. Same as 7858 immersion well, except, plain-sided, (without standard taper joint), for use with #50 Screw thread bushing and all 7863, 7864, and 7865 vessels. 415mm total jacket length. Will accommodate 7858-85 and -88 inner tubes.