The specific experimental rules that MLB is having tested in the independent Atlantic League this season have been announced:
Home plate umpire assisted in calling balls and strikes by a TrackMan radar tracking system.
No mound visits permitted by players or coaches other than for pitching changes of medical issues.
Pitchers must face a minimum of three batters, or reach the end of an inning before they exit the game, unless the pitcher becomes injured.
Increase the size of 1st, 2nd and 3rd base from 15 inches square to 18 inches square.
Require two infielders to be on each side of second base when a pitch is released (if not, the ball is dead and the umpire shall call a ball).
Time between innings and pitching changes reduced from 2:05 to 1:45.
Distance from pitching rubber to home plate extended 24 inches, in the second half of the season only; with no change to mound height or shape.