The M18 18-Volt Lithium-Ion Compact Rechargeable Battery delivers more run time, power and speed than standard lithium-ion batteries. This REDLITHIUM battery was designed with best-in-class pack construction, technology and performance for optimal work per charge and work over pack life. Use this 27-watt-hour battery to power more than 40 Milwaukee M18 cordless power tools. This versatility saves you money.