xxxxxxxxxx
a device for controlling the passage of fluid or air through a pipe, duct, etc., especially an automatic device allowing movement in one direction only.
xxxxxxxxxx
a device for controlling the passage of fluid or air through a pipe, duct, etc., especially an automatic device allowing movement in one direction only.
xxxxxxxxxx
a device for controlling the passage of fluid or air through a pipe, duct, etc., especially an automatic device allowing movement in one direction only.