look up the definition of restric... IE.. it slows.
It might be used to keep a cyl from moving slow and not slapping back / forth due to the 'full flow' from the circuit being bottleknecked thru a small orifice.
other things you can find in some valves. are check circuits.. these prevent cyls from dropping when they are not suposed to. many 'manlift' hyd systems have piloted checks right at the cyls, so even if a hose breaks at the cyl, the cyl doesn't drop.. etc.
soundguy