[EN 12792-2003, 244]:algebraic difference between the minimum limit of size and the corresponding nominal size.

[EN 12792-2003, 245]:short circular sleeve used to join two pieces of spiral duct together. The ends of the male connector are inserted into the spiral tube ends.

[EN 12792-2003, 247]:device which can be used to manually adjust the air flow rate.(see also damper and valve)