help with slave/master cylinder!?!?!?

im putting a whole new unit on my 98 xj and i have one quick question on the bottom of the slave cylinder where it connects to the bell housing there is a little gold screw in my old one and the new unit i purchased from the stealership does not have one in it should i put the old screw in the new unit im not sure what it does

would anybody happen to know??

thanks