Centering with external centering rings is effected on the external diameter of the small flange, the O-ring seal is pressed into an internal radius.

• NBR O-rings can be used in −25 to +80 °C; FPM O-rings can be used from −40 to +150 °C
• With external centering, the same ring can be used for two nominal widths
• No gaps are present on the vacuum side

PBT, with O-ring seals made from NBR or FPM.