Stadiums are outfitted with cameras that track each pitch and judge whether it crossed home plate within the strike zone. While the strike zone actually called by big league umpires tends to be oval in shape, the ABS strike zone is a rectangle, as in the rule book. Developing a consensus on what a computer strike zone should be has been an issue. So what is the MLB strike zone? Narrowing the strike zone led to an increase in walks and only small changes in strikeout rates.