I had an ST4 before I got my 996, and the ST comes with rubber grommets plugging the frame tube ends. A couple of minutes with a micrometer in the local dealer's showroom enabled me to source all the plugs I needed for the 996 from the ST catalogue, at about £1 each, except for the swinging arm support tubes, but as I use these holes to support the bike on a centre stand, I just left them open.