There are slight differences between Japanese Nippon League Baseball rules and American Major League Baseball rules, with the main difference being that Japanese baseball allows ties and limits game length, as of April 2015. Japanese baseball teams are limited to four foreign players on their 25 player game rosters.
Technical elements that differ between Japanese and American baseball are the ball, the strike zone and the field. The ball is smaller, more tightly wound and harder than an American baseball. The strike zone narrows toward the batter. The team fields don't have to meet the same size minimums as American teams.
Inning limits for Japanese baseball are 12 innings for regular season games and 15 innings for playoff games. If a game continues for three hours and 30 minutes after the first pitch, the current inning becomes the final inning.
Japanese baseball players tend to focus more on sacrifice flies, bunts, walks, effective fielding and stealing bases than American baseball players. Common etiquette among Japanese players is for the pitcher to tip his cap if he accidentally hits the batter. This indicates that it wasn't an intentional hit.
The Nippon Professional Baseball League is Japan's highest level of baseball. It has two leagues, the Central League and the Pacific League. The winners from each league compete in the Japan Series for the league's championship.