The PzKpfw III Ausf M was introduced in 1942 as a variant of the Ausf L with modifications to allow for mass production. The hull vision ports and escape doors were eliminated, which allowed for a redistribution of ammunition stowage and an increase in 50-mm rounds from 50 to 98. Although the removal of the hull escape doors may seem like a step back, it was necessary to accommodate essential skirt armor. In addition to this, the Ausf M had a wading capability of 1.5 meters and a valve system that allowed the transfer of hot engine coolant to other tanks with the same system. This system was introduced in response to conditions on the Eastern Front, where tanks had difficulty starting in cold weather. The Ausf M was able to warm up another tank’s engine in as little as 12-15 minutes, making start-ups easier in extreme temperatures. Despite production continuing into early 1943, the first examples of the ultimate PzKpfw III variant had already appeared in 1942.