On the BorgWarner S300 series turbos there is a port for a speed sensor. Most don't need this option so BorgWarner makes it a blind hole that requires drilling thru it to make it functional. But once the turbo is mounted into your vehicle the open space there on the compressor side just seems to mock you. Instead there is now a Wits' End block-off plate to cover up those open holes and give the turbo a more finished look.
MADE in USA