Fit for RYOBI 40V Lithium tools and Ryobi 40V lithium charger OP401/ZROP401. The 40V Lithium-ion Battery is the perfect addition to your RYOBI 40V tool collection. The 40-volt 4.0Ah high-power lithium battery with built-in LED indication extends operating time, which is 2 times longer than the standard 2.6Ah.