The M4A1 was a halftrack used by the US Army during WWII, designed for use as a self-propelled mortar. It carried an 81mm mortar in the rear of the vehicle along with up to 112 rounds of ammunition.Model features detailed mortar compartment with 81mm mortar, .30 cal machine gun, and seats; separate road wheels and suspension arms; detailed cab with fold-down windshield, steering wheel and driver figure; 1-piece molded, flexible, vinyl tracks.