Free flow in one direction and restricted in reverse.
The restriction is set by the hole diameter in the throttle valve and therefore it is fixed.
V0590/1F, V0600/1F, V0610/1F, V0620/1F, V0630/1F, V0631/1F, V0632/1F, V0590/2F, V0600/2F, V0610/2F, V0620/2F, V0630/2F, V0631/2F, V0632/2F