One example of the increased firepower provided by modern mobile howitzers is the latest version, the "G6-52", of the 155 mm G6 howitzer. It can fire up to six rounds in quick succession that will land nearly simultaneously. This is achieved by firing the shells at different trajectories so that the first round has the longest flight time and the last round the shortest. This is an improvement of the concept of MRSI (Multiple Rounds Simultaneous Impact), itself an enhancement of the earlier TOT (Time On Target) concept. The necessary rapid reloading is made possible by an automated ammunition feed system.