NewerTech and Other World Computing (OWC) on Thursday introduced their highest capacity PowerBook G4 replacement battery to date. The battery features a 55.5 watt hour capacity, almost 16 percent more than Apple’s factory-shipped batteries, according to Newer. The NuPower battery costs $139.99.

The new NuPower lithium-ion battery is designed for Apple’s 15-inch aluminum-clad PowerBook G4 models, and is compatible with all 15-inch aluminum models clocked from 1.0GHz to 1.67GHz. It uses battery cell technology not available through other manufacturers in this capacity, according to the company.

NewerTech and OWC also offer a 53.3 watt hour model for $129.99.