Benoil makes a range of standard products which keeps growing. We characterise
these for easy reference by a nominal bore size, which for historical reasons
is given in metric in small sizes and in imperial in the larger.
An alternative description is by a thread size, but neither is adequate in
isolation. For example, there are two possible threads available on the
1-1/2" bore. Other design features may also mean that shorthand
descriptions are insufficient, eg whether the O-ring is carried or fits
to a chamfer. Some are available also with a choice of foils.