Most of the 13,000 M113s that are still in U.S. Army service have been upgraded to the A3 variant. The current U.S. Army M113 fleet includes a mix of M113A2 and A3 variants and other derivatives equipped with the most recent RISE (reliability improvements for selected equipment) package. The standard RISE package includes an upgraded propulsion system (turbocharged engine and new transmission), greatly improved driver controls (new power brakes and conventional steering controls), external fuel tanks, and 200-amp alternator with four batteries. Additional A3 improvements include the incorporation of spall liners and provision for mounting external armor.