jammers correct, no zerk is NORMAL on the a/s cup.
so some1 added this to your trailer.
given how infrequently and how easy greasen' the ball is...
no zerk is needed
also this doesn't make CLEANING the cup easier.
we've discussed this in other threads...
read 5 posts (#222-226) here...
last post has a PHOTO with zerk added.
the problem is, NOW the cups gotta HOLE in it.
so either PLUG it or tap/thread correctly and add another zerk.
the lectric screw stab/jacks on your unit may have ZERKS for lubn (mine sure do)
so pick one the SAME SIZE and the grease gun tip does multi duty.