rtmoore4,
I think it was a #4, but there is no marking on the sleeve.
However, even after trimming the leading edge, I found the sleeve would squirm around just enough to preload the magazine in the "eject" direction. And the mag ejected itself twice at the range. I pulled the sleeve off. The mag(s) behaved for the rest of the session, and ever since.
So, back to the skateboard tape. It's non-intrusive and works fine for me.
Steve