A deceleration valve is a cam operated two-way valve with a tapered spool. As the cam depresses the plunger, folw through the valve is gradually decreased to the cut off point.  This valve is a normally closed so as the cam is pushed in the flow path is opened. It still has to go through the needle valve so the valve can be adjusted to a maximum flow if desired.  Maximum pressure is 3000 psi and maximum gpm of 19 gpm.