Apex Instruments offers Button-Hook Nozzles in multiple materials. The size needed for isokinetic sampling depends on the stack gas velocity; the material depends on the stack temperature and the sampling method. The most popular nozzles are constructed from seamless 316 stainless steel and can be coated with FEP or SilcoSteelCR®. Other nozzle materials include Borosilicate Glass, Alloy 600 and Quartz. Standard sampling nozzles are 4" long and have a 5/8" o.d. shank for attaching to the probe union. Stainless steel nozzles are configured with an O-Ring to aid in positive leak checks. A bored out union is needed with Apex O-Ring nozzles, although a standard union can be used if the O-Ring is removed. Other sizes and configurations are available. Nozzles must be measured before initial use. Glass and Quartz Nozzles are available with a female 14/35 ground glass taper joint eliminating the need for the 5/8" union. For use with male taper joint probe liners