By the end of the war the variety in tank designs was narrowed and the concept of the main battle tank emerged. After World War II, the race to increase caliber slowed. Slight increases were made between tank generations. In the West, guns of around 90 mm gave way to the ubiquitous 105 mm L7. This lasted a long while with a shift to 120 mm in the late 1970s and early 80s (the UK changed in the late 60s with their Chieftain tank). In the East, the 85 mm quickly yielded to the 100 mm and 115 mm U-5TS gun, with the 125 mm caliber now standard. Most of the improvements were instead made in ammunition and fire control systems.