To go to the site where I got this illustration, click here.  They use fairly graphic illustrations on this site, but
nothing overtly sexual in nature.  It is a medical site, so anatomically correct terminology is used with many
links and references provided.  This illustration shows the mechanics of vaginal penetration with an
uncircumcised, uncut or restored penis.
Notice that the glans of the penis
is barred upon insertion, but the
shaft skin covers the corona and
glans when sliding out.  This
protects the corona from over
stimulation.  This means that you
might no longer suffer from
pre-mature ejaculation if you
have this covering back.  I know
first hand.  I'm growing mine back.