Because it was unusually low to the playing field, the air-inflated dome occasionally figured into game action during baseball games. Major League Baseball had specific ground rules for the Metrodome. Any ball which struck the Dome roof, or objects hanging from it, remained in play; if it landed in foul territory it became a foul ball, if it landed in fair territory it became a fair ball. Any ball which became caught in the roof over fairground was a ground rule double. That has only happened three times in its history – Dave Kingman for the Oakland Athletics on May 4, 1984, the University of Minnesota Gophers player George Behr and Corey Koskie in 2004. The speakers, being closer to the playing surface, were hit more frequently, especially the speakers in foul ground near the infield, which were typically hit several times a season, which posed an extra challenge to infielders trying to catch them. However, beginning with the 2005 season, the ground rules for Twins games were changed such that any batted ball that struck a speaker in the foul territory would automatically be called a foul ball, regardless of whether or not it was caught.