18V, 4.0Ah, Lithium-Ion Battery, Unbeatable 36 Minute Charge Time, Lightweight & Shock-Absorbing, Works With Current Lithium-Ion Chargers, Longer Run Time & Battery Life, Foam Cell Technology, Will Not Puncture & Remains Cool Even In Heavy Use, All New 4.0Ah Models Are Compatible With 18V 3.0Ah Lithium-Ion Batteries.